Next Article in Journal
A Fundamental Reason for the Need of Two Different Semiconductor Technologies for Complementary Thin-Film Transistor Operations
Next Article in Special Issue
Structure of a Luminescent MOF-2 Derivative with a Core of Zn(II)-Terephthalate-Isoquinoline and Its Application in Sensing of Xylenes
Previous Article in Journal
Two Interpenetrated Zn(II) Coordination Polymers: Synthesis, Topological Structures, and Property
Previous Article in Special Issue
A Newly Synthesized Heterobimetallic NiII-GdIII Salamo-BDC-Based Coordination Polymer: Structural Characterization, DFT Calculation, Fluorescent and Antibacterial Properties
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Crystals
Volume 9
Issue 11
10.3390/cryst9110602
crystals-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Fluorescence Properties and Density Functional Theory Calculation of a Structurally Characterized Heterotetranuclear [ZnII2–SmIII2] 4,4′-Bipy-Salamo-Constructed Complex

by
Xiao-Xin An
,
Chang Liu
,
Zhuang-Zhuang Chen
,
Ke-Feng Xie
and
Yang Zhang
*
School of Chemical and Biological Engineering, Lanzhou Jiaotong University, Lanzhou730070, China
*
Author to whom correspondence should be addressed.
Crystals 2019, 9(11), 602; https://doi.org/10.3390/cryst9110602
Submission received: 27 October 2019 / Revised: 14 November 2019 / Accepted: 14 November 2019 / Published: 17 November 2019
(This article belongs to the Special Issue Fluorescent Complexes)
Browse Figures
Versions Notes

Abstract

:
A new heterotetranuclear complex, [{Zn(L)Sm(NO3)3}2(4,4′-bipy)]·2CH3OH, was synthesized via an unsymmetrical single salamo-like ligand H2L: 6-methoxy-6′-ethoxy-2,2′-[ethylenedioxybis(azinomethyl)]diphenol, with Zn(OAc)2·2H2O, Sm(NO3)3·6H2O, and 4,4′-bipyridine by the one-pot method. The [ZnII2–SmIII2] complex was validated via elemental analysis, powder X-ray diffraction (PXRD) analysis, infrared spectroscopy, and ultraviolet–visible (UV–Vis) absorption spectroscopy. The X-ray single crystal diffraction analysis of the [ZnII2–SmIII2] complex was carried out via X-ray single-crystal crystallography. The crystal structure and supramolecular features were discussed. In addition, while studying the fluorescence properties of the [ZnII2–SmIII2] complex, the density functional theory (DFT) calculation of its structure was also performed.

Graphical Abstract

1. Introduction

Self-assembly in coordination chemistry refers to the acquisition of a multinuclear complex or polymer by the reaction of a metal ion with an organic ligand [1,2,3,4,5,6,7,8]. The choice of organic ligand tends to be a polydentate nitrogen-containing ligand, a polydentate carboxylic acid ligand, or a polydentate carboxylic acid pyridine ligand. These ligands can be directly self-assembled with transition/rare-earth metal ions to give the corresponding homopolynuclear complexes or polymers. They can also be assembled as auxiliary ligands into a heteropolynuclear complex or polymer in the form of bridges, or even constitute Metal Organic Frameworks (MOFs). Many homopolynuclear or heteropolynuclear complexes have been studied with salen-like or salamo-like complexes [9,10,11,12,13,14,15,16,17]. In addition to potential applications in the fields of magnetism [18,19,20,21,22,23,24,25], catalysis [26,27], biology [28,29,30,31,32], electrochemical research [33,34,35,36,37], functional [38,39,40] and nonlinear optical materials [41,42,43,44,45,46,47], such complexes also play an important role in the field of supramolecular building [48,49,50,51] and sensors [52,53,54,55,56]. The luminescence of rare-earth complexes has been a hot area for researchers due to its excellent application value in lasers, sensing, and fluorescence imaging. Therefore, designing and self-assembling heteropolynuclear salamo-like complexes containing auxiliary ligands with good fluorescence properties is a major challenge for researchers today.
It is not surprising that, in the past few years, rare-earth metal ions have been introduced into the coordination of organic compounds [57,58,59], and a large number of heterobimetallic 3d-4f salamo-like complexes have also been reported [60,61,62,63,64]. However, heterobimetallic 3d-4f salamo-like complexes containing auxiliary ligands have rarely been investigated [65]. Here, a polydentate nitrogen-containing ligand was used as an auxiliary ligand in the synthesis of a heterobimetallic 3d-4f salamo-like complex, and a newly designed tetranuclear [ZnII2–SmIII2] salamo-like complex was successfully assembled by a one-pot reaction of H2L, Zn(OAc)2·2H2O, Sm(NO3)3·6H2O, and 4,4′-bipyridine. The [ZnII2–SmIII2] complex was validated by elemental analysis, powder X-ray diffraction (PXRD) analysis, infrared and UV–Vis absorption spectroscopy. At the same time, fluorescent print imaging and the density functional theory (DFT) calculation were performed.

2. Experimental

2.1. General Details

2-Hydroxy-3-Methoxybenzaldehyde (99%) was purchased from Meryer Chemical Technology Co., Ltd., 3-Ethoxysalicylaldehyde (>97%) was purchased from Tokyo Chemical Industry Co., Ltd., and other reagents and solvents were purchased from the Tianjin Chemical Reagent Factory and used as received without further purification. X-ray single-crystal diffraction data of the [ZnII2–SmIII2] complex were measured and recorded using a Bruker APEX-II CCD surface inspection diffractometer (Bruker, Germany). The PXRD experiment with the [ZnII2–SmIII2] complex was recorded in the range of 2θ = 5–50° using a D/max-2400 powder X-ray diffractometer (Rigaku, Japan). The fluorescence lifetime of H2L and the [ZnII2–SmIII2] complex were measured using a FLS920 time-resolved fluorescence spectrometer (Edinburgh, United Kingdom). DFT calculations were performed on H2L and the [ZnII2–SmIII2] complex using the Gaussian 09 software package [33,35,47,54]. The test methods of other instruments used in this paper are the same as those in the previous literature [27,66].

2.2. Synthesis of H2L

As depicted in Scheme 1, 1,2-bis(aminooxy)ethane was obtained according to a previously reported method [66]. 2-Hydroxy-3-Methoxybenzaldehyde (304.3 mg, 2.0 mmol) in an ethanol solution (50 mL) was slowly added to an ethanol solution (15 mL) of 1,2-bis(aminooxy)ethane (368.4 mg, 4.0 mmol). The mixed solution was stirred at 45–55 °C for 4 hours and distilled under reduced pressure. The residue was purified by column chromatography (dichloromethane:ethyl acetate = 15:1) to acquire a white crystalline solid of 2-[O-(1-ethoxyamide)]oxime-6-methoxyphenol [67]. Yield: 69.7%. m.p: 93−94 °C. Anal. Calcd for C10H14N2O4 (%): C, 53.09; H, 6.24; N, 12.38. Found: C, 53.22; H, 6.11; N, 12.32.
An ethanol solution (50 mL) of the obtained 2-[O-(1-ethoxyamide)]oxime-6-methoxyphenol (452.4 mg, 2.0 mmol) was added to an ethanol solution (30 mL) of 3-Ethoxysalicylaldehyde (332.3 mg, 2.0 mmol). The mixed solution was stirred at ca. 55 °C for about six hours, concentrated under reduced pressure, and a white crystalline powder H2L was obtained. Yield: 83%. m.p: 100−101 °C. Anal. Calcd for C19H22N2O6 (%): C, 60.95; H, 5.92; N, 7.48. Found: C, 61.02; H, 5.89; N, 7.41. 1H NMR (400 MHz, CDCl3) δ 9.73 (s, 1H, –OH), 9.69 (s, 1H, –OH), 8.26 (s, 2H, –N=CH), 6.91 (dd, J = 7.2, 2.8Hz, 2H, –ArH), 6.88–6.80 (m, 4H, –ArH), 4.47 (t, J = 4.2 Hz, 4H, –CH2), 4.11 (q, J = 8.4 Hz, 2H, –OCH2), 3.91 (s, 3H, –OCH3), 1.48 (t, J = 5.6 Hz, 3H, –CH3). IR (KBr, cm–1): 3427 (vs), 2978 (w), 2930 (m), 2876 (w), 2835 (w), 2073 (m), 1613 (vs), 1468 (s), 1420 (w), 1386 (w), 1352 (m), 1250 (vs), 1059 (vs), 985 (m), 733 (m), 638 (s), and 488 (m). UV–Vis (CH3CH2OH), λmax (nm) [(εmax): (dm3 mol−1 cm−1)]: 270 and 319 nm (1.0 × 10−5 M).

2.3. Synthesis of the [ZnII2–SmIII2] Complex

A solution of H2L (7.5 mg, 0.02 mmol) in dichloromethane (2 mL) was added to Zn(OAc)2·2H2O (4.50 mg, 0.02 mmol) and Sm(NO3)3·6H2O (9.0 mg, 0.02 mmol) in methanol (4 mL). After the mixture was stirred for about 10 minutes, a solution of 4,4′-bipyridine (3.50 mg, 0.02 mmol) in methanol (2 mL) was added and continued to be stirred for an additional 10 minutes. The mixture was filtered off and the filtrate was sealed with a foil paper. It was placed in an undisturbed environment for about two weeks, and transparent white block-like single crystals suitable for X-ray crystallographic analysis were obtained. Anal. Calcd for [{Zn(L)Sm(NO3)3}2(4,4′-bipy)]·2CH3OH (C50H56N12O32Sm2Zn2) (%): C, 33.96; H, 3.19; N, 9.50; Sm, 17.00; Zn, 7.39. Found: C, 33.99; H, 3.05; N, 9.44; Sm, 17.32; Zn, 7.43. IR (cm−1, KBr): 3400 (vs), 2984 (m), 2937 (w), 2359 (w), 2076 (m), 1604 (vs), 1461 (w), 1372 (m), 1284 (w), 1273 (w), 1216 (m), 1063 (s), 788 (m), 723 (s), 624 (s), 512 (m), and 478 (m). UV–Vis (CH3CH2OH), λmax (nm) [(εmax): (dm3 mol−1 cm−1)]: 273 and 343 nm (1.0 × 10−5 M).

2.4. X-ray Crystallography Analysis

The description of X-ray crystallography is presented in the Supplementary Information (SI). Crystallographic data of the [ZnII2–SmIII2] complex and the refinement parameters are presented in Table 1. CCDC: 1959376.

3. Results and Discussion

3.1. PXRD Analysis

The PXRD experiment with the [ZnII2–SmIII2] complex was performed with an X-ray diffractometer using Cu-Kα radiation (λ = 0.154 nm) in the range of 2θ = 5–50°. A comparison of the simulated and experimental PXRD patterns of the [ZnII2–SmIII2] complex is shown in Figure 1. The experimental pattern was in good agreement with the simulated pattern, which confirmed the phase purity and isomorphism of the [ZnII2–SmIII2] complex. It further illustrated that the [ZnII2–SmIII2] complex had sufficient purity to be used to study its spectral characteristics and fluorescence properties.

3.2. IR Spectra

The infrared spectra of H2L and the [ZnII2–SmIII2] complex are shown in Figure S1 (Supplementary Materials) and Table 2. The O–H stretching vibration of the phenolic hydroxyl group of the ligand H2L exhibited a strong band at about 3427 cm−1, and at the same time, the [ZnII2–SmIII2] complex exhibited a strong absorption band at about 3400 cm−1 due to the O–H stretching vibration band on the crystalline methanol molecules, which was consistent with the results of the element analysis. A stretching vibration band of the free ligand H2L was observed at 1613 cm−1, which corresponds to the stretching vibration band of the C=N double bond. That of the [ZnII2–SmIII2] complex was observed at 1604 cm−1 because the N atom provided a lone pair of electrons to the ZnII ions, thereby reducing the bond intensity of the C=N double bond and causing a red shift, indicating that the nitrogen atoms of the C=N double bond in H2L were coordinated with the ZnII ions. In addition, a typical Ar–O stretching vibration band was observed at 1250 cm−1 in the spectrum of the free ligand H2L. The Ar–O stretching band shifted to a lower frequency of about 1216 cm−1 in the spectrum of the [ZnII2–SmIII2] complex, indicating that M–O bonds were formed between the phenolic oxygen atoms and the metal (II/III) ions.

3.3. UV–Vis Spectra

The UV–Vis absorption spectra of H2L and the [ZnII2–SmIII2] complex were measured at room temperature in concentrations of 1.0 × 10−5 M, respectively. As depicted in Figure 2, the absorption spectrum of H2L mainly exhibited two relatively strong absorption peaks, which appeared at approximately 270 and 319 nm. The former absorption peak at 270 nm was part of the π–π* transition of the benzene ring conjugate system, while the latter absorption peak at 319 nm was part of the π–π* transition of the chromophore C=N groups. In the [ZnII2–SmIII2] complex, the absorption peak formed by the π–π* transition of the benzene ring conjugate system still existed, but only moved to a high wave number at 3 nm. The absorption peak at 319 nm disappeared, and a new absorption peak appearing at approximately 343 nm was found in the [ZnII2–SmIII2] complex. This peak may be part of the L⟶M charge–transfer transition [68], which is characteristic absorption peak of an N2O2-donor metal complex.

3.4. Crystal Structure and Supramolecular Interactions

As depicted in Figure 3a, two chemically and crystallographically identical dinuclear [Zn(L)Sm] units and one 4,4′-bipyridine linker were self-assembled to obtain a heterotetranuclear [ZnII2–SmIII2] salamo-like complex [{Zn(L)Sm(NO3)3}2(4,4′-bipy)]·2CH3OH. The coordination polyhedrons are depicted in Figure 3b. The coordination environments of the two ZnII and SmIII ions were the same in each heterobinuclear [Zn(L)Sm(NO3)3] unit. Compared with the previously reported Salamo-type Zn–La complex [65], the coordination environments of ZnII ions are similar, while the coordination environments of SmIII ions are different. The penta-coordinated ZnII ion (Zn1) was located at the N2O2 coordination cavity (N1, N2, O2, and O5) of the (L)2− unit, and the axial position was occupied by the nitrogen atom (N6) of 4,4′-bipyridine, bearing a slightly twisted square pyramidal coordination geometry with τ = 0.1845 [27,69]. The four atoms (N1, N2, O2, and O5) in the N2O2 cavity of the ligand formed an equatorial plane of the square pyramid, and the nitrogen atom (N6) on the pyridine ring occupied the apex of the square pyramid. The deca-coordinated SmIII ion (Sm1) was coordinated to the O4 coordination environment (O2, O5, O1, and O6) of the (L)2− unit, and the six oxygen atoms (O7, O8, O10, O11, O13, and O14) from the three bidentate nitrates. Therefore, the SmIII ion (Sm1) bore a twisted double-capped tetragonal anti-prism geometry. The 4,4′-bipyridine was located in the inversion center of two heterobinuclear [Zn(L)Sm(NO3)3] units. Referring to Figure S2, the dihedral angle of the two pyridine rings (N6–C20–C21–C22–C23–C24 and N6#1–C20#1–C21#1–C22#1–C23#1–C24#1) of 4,4′-bipyridine was about 36.33(5)°, exhibiting that the two pyridine rings were non-planar. This result was different from the coplanarity of the two pyridine rings in the Zn–La complex, which indirectly indicated that the formation process of the [ZnII2–SmIII2] complex was more prone to torsion and had a better chance of forming a novel structure complex. Symmetry transformations were used to generate equivalent atoms: #1 1 − x, + y, 1/2 − z. The essential bond lengths and angles of the [ZnII2–SmIII2] complex are summarized in Table S1.
For the supramolecular structure of the [ZnII2–SmIII2] complex, the relevant data are summarized in Table 3. There were two pairs of intramolecular hydrogen-bonding interactions (C20–H9B···O13 and C24–H24···O4) in the [ZnII2–SmIII2] complex, as depicted in Figure 4a,b. The [ZnII2–SmIII2] complex included four pairs of intermolecular hydrogen-bondings (C12–H12···O9, C23–H23···O11, C23–H23···O14, and C24–H24···O11), with C23–H23 and C24–H24 of the pyridine ring and C12–H12 on the C=N group acting as donors for the hydrogen-bondings, and the oxygen atoms on the bidentate nitrate groups serving as hydrogen-bonding acceptors [70]. A structurally stable two-dimensional (2-D) supramolecular structure was formed along the alternating current (ac) direction via intermolecular hydrogen-bonding interactions. As depicted in Figure 4c, finally, a three-dimensional (3-D) central perspective structure was formed.

3.5. Fluorescent Properties

The solid fluorescence spectrum of the [ZnII2–SmIII2] complex is shown in Figure 5. This emission spectrum showed that the [L-Zn2+] units and rare-earth ions (SmIII) exhibited co-luminescence in the solid state.
The ethanol solutions of H2L and the [ZnII2–SmIII2] complex were prepared in concentrations of 1.0 × 10−5 M, respectively, and the fluorescence spectra were measured at an excitation wavelength of 320 nm at room temperature (Figure 6a). When the excitation wavelength was 320 nm, the emission spectrum of the ligand H2L exhibited a broad emission band at 397 nm, which can be assigned to the π–π* transitions in the ligand H2L. For the [ZnII2–SmIII2] complex, in addition to a large broad peak at 401 nm, several visible emission bands of SmIII ions as the lanthanide ions were observed at 564, 598, and 644 nm. These peaks correspond to the energy level transitions of 4G5/2-6HJ (J = 5/2, 7/2, 9/2), respectively. The appearance of characteristic emission peaks indicated that the ligand H2L can act as an antenna group, sensitizing the emission of SmIII ions through the [L-Zn2+] units, thereby making the luminescence of SmIII ions sensitive [27].
The fluorescence titration spectra of H2L and the [ZnII2–SmIII2] complex in ethanol solution are depicted in Figure 6b,c. In the fluorescence titration experiment with the [ZnII2–SmIII2] complex, the fluorescence emission peak intensity decreased gradually during the addition of ZnII ions (1.0 × 10−3 M) to the free ligand H2L (1.0 × 10−5 M). When ZnII ions started from 5 μL and gradually increased to 55 μL in increments of 5 μL, the fluorescence intensity began to stabilize and the titration reached the end point, indicating that the coordination of ZnII ions with H2L was completed and the stoichiometric ratio was 1:1. Immediately thereafter, when the amount of SmIII ions added reached the equivalent of 1.0 equivalent, the fluorescence intensity was no longer lowered, indicating the coordination of the SmIII ions with the [L-Zn2+] units. This titration curve also clearly indicated that the stoichiometric ratio of H2L:ZnII:SmIII was 1:1:1. This result also corresponds to the coordination of the actually obtained crystal structure.

3.6. Fluorescence Print Imaging

From the fluorescence spectra, SmIII ions were effectively sensitized, and exhibited characteristic excitation and emission spectra, so the [ZnII2–SmIII2] complex had the pink light that is characteristic emission of SmIII ions. Therefore, we attempted to refer this special property to fluorescent print imaging. As shown in Figure 7, the fluorescence lifetime was measured to further investigate the luminescent properties of H2L and the [ZnII2–SmIII2] complex. It was determined from the correlation data of the spectrua that the fluorescence lifetime of H2L was 1.5222 ns, and for the [ZnII2–SmIII2] complex, the decay of the excited state became shorter (1.5048 ns). Two bottles with the same concentrations (2.5 × 10−5 M) and volumes of the ligand H2L and the [ZnII2–SmIII2] complex were selected as research objects. Under natural light, both the ligand H2L and the [ZnII2–SmIII2] complex exhibited a colorless and transparent state (Figure 8a). Under 365 nm ultraviolet (UV) light, the ligand H2L showed a pale light, at which time the [ZnII2–SmIII2] complex showed a pink light distinctly from the ligand, as depicted in Figure 8b. These excellent optical properties could easily allow for the [ZnII2–SmIII2] complex to be used in fluorescent print imaging under specific conditions. Compared to many other nanoparticle inks, the [ZnII2–SmIII2] complex had a lower concentration (0.44 mg/mL) [71,72,73], which also reflects the environmental friendliness and economy of selecting such a complex.
In order to reduce the interference from background UV fluorescence, a non-fluorescent filter paper was used as the printing paper. The fluorescent imaging of H2L and the [ZnII2–SmIII2] complex solutions as the ink are shown in Figure 8c,d. The word "Crystals" was marked with each of the H2L and the [ZnII2–SmIII2] complex on the same filter paper and dried in an oven. When observed under 365 nm UV light, there was almost no pattern at the mark with the ligand solution, and a pink image of "Crystals" was displayed at the mark with the [ZnII2–SmIII2] complex. This further confirmed that the [ZnII2–SmIII2] complex can be used to create a fluorescent print imaging.

3.7. DFT Calculation

Molecular orbital calculations were performed by density functional theory. The DFT method used was the gradient-corrected functional proposed by B3LYP, and basis sets with SDD were used to expand the Kohn–Sham orbitals. Surface plots of some selected molecular orbitals of H2L and the [ZnII2–SmIII2] complex are shown in Figure 9. It is worth noting that the HOMO and LUMO of the [ZnII2–SmIII2] complex were detected in both ligands; while the HOMO–1 was mainly concentrated in one of the two ligands, the LOMO+1 was mainly distributed in the orbit of 4,4′-bipyridine. Compared with the ligand H2L, the molecular orbital energies occupied by the [ZnII2–SmIII2] complex are all negative, indicating that it is more chemically stable. The frontier molecular orbital energies of the ligand H2L are EHOMO = –2.6563 eV and ELUMO = –0.4351 eV. The frontier molecular orbital energies of the [ZnII2–SmIII2] complex are EHOMO = –5.3891 eV and ELUMO = –5.2017 eV. The energy gap (ΔE = ELUMO – EHOMO) between the HOMO and LUMO of the [ZnII2–SmIII2] complex was 0.1874 eV, which was lower than that of the ligand H2L (2.2212 eV). Based on these results, electrons are more likely to transition during the formation of the [ZnII2–SmIII2] complex, resulting in a more active complex.

4. Conclusions

A heterotetranuclear 3d-4f complex was prepared and characterized structurally. In the [ZnII2–SmIII2] complex, the auxiliary ligand 4,4′-bipyridine acted as a bidentate connecting rod, introducing its pyridine nitrogen atoms, which tended to coordinate with the axial position of the ZnII ions, further linking the two [Zn(L)Sm] units. The ZnII ion (Zn1) was located in the coordination environment of the N2O2 donor and considered to have a twisted square pyramidal geometry (τ = 0.1845). In addition, sensitizing the emission of SmIII ions through the [L–Zn2+] units, the [ZnII2–SmIII2] complex exhibited a pink characteristic fluorescence that can be applied to fluorescent print imaging under specific conditions. The molecular orbital energy levels of the ligand H2L and the [ZnII2–SmIII2] complex were discussed by DFT calculation. The calculated results further indicated that the lower the energy gap, the more active and the easier it is to develop in a stable direction.

Supplementary Materials

The following are available online at https://www.mdpi.com/2073-4352/9/11/602/s1, Figure S1: Infrared Spectra of H2L and its [ZnII2-SmIII2] complex, Figure S2: The dihedral angle between the planes of the two pyridine rings of the [ZnII2-SmIII2] complex, Table S1: Essential bond lengths (Å) and angles (°) of the [ZnII2-SmIII2] complex.

Author Contributions

Y.Z. conceived and designed the experiments and contributed reagents/materials/analysis tools; X.-X.A., C.L. and Z.-Z.C. performed the experiments; C.L., Z.-Z.C. and K.-F.X. analyzed the data; X.-X.A. and Y.Z. wrote the paper.

Funding

This work was supported by the National Natural Science Foundation of China (Grant No. 21761018) and the Program for Excellent Team of Scientific Research in Lanzhou Jiaotong University (Grant No. 201706).

Acknowledgments

Computations were done at the National Supercomputing Center in Shenzhen, P. R. China.

Conflicts of Interest

The authors declare no competing financial interests.

References

  1. Akine, S.; Nabeshima, T. Cyclic and acyclic oligo(N2O2) ligands for cooperative multi-metal complexation. Dalton Trans. 2009, 47, 10395–10408. [Google Scholar] [CrossRef]
  2. Amirkhanov, O.V.; Moroz, O.V.; Znovjyak, K.O.; Sliva, T.Y.; Penkova, L.V.; Yushchenko, T.; Szyrwiel, L.; Konovalova, I.S.; Dyakonenko, V.V.; Shishkin, O.V.; et al. Heterobinuclear Zn-Ln and Ni-Ln complexes with Schiff-base and carbacylamidophosphate ligands: Synthesis, crystal structures, and catalytic activity. Eur. J. Inorg. Chem. 2014, 23, 3720–3730. [Google Scholar] [CrossRef]
  3. Zhang, H.J.; Chang, J.; Jia, H.R.; Sun, Y.X. Syntheses, supramolecular structures and spectroscopic properties of Cu(II) and Ni(II) complexes with Schiff base containing oxime group. Chin. J. Inorg. Chem. 2018, 34, 2261–2270. [Google Scholar]
  4. Akine, S.; Taniguchi, T.; Matsumoto, T.; Nabeshima, T. Guest-dependent inversion rate of a tetranuclear single metallohelicate. Chem. Commun. 2006, 47, 4961–4963. [Google Scholar] [CrossRef] [PubMed]
  5. Chang, J.; Zhang, H.J.; Jia, H.R.; Sun, Y.X. Binuclear nickel(II) and zinc(II) complexes based on 2-amino-3-hydroxy-pyridine Schiff base: Syntheses, supramolecular structures and spectral properties. Chin. J. Inorg. Chem. 2018, 34, 2097–2107. [Google Scholar]
  6. Costes, J.P.; Donnadieu, B.; Gheorghe, R.; Novitchi, G.; Tuchagues, J.P.; Vendier, L. Di- or trinuclear 3d-4f Schiff base complexes: The role of anions. Eur. J. Inorg. Chem. 2008, 33, 5235–5244. [Google Scholar] [CrossRef]
  7. Guo, J.Q.; Sun, Y.X.; Yu, B.; Li, J.; Jia, H.R. Syntheses, crystal structures and spectroscopic properties of copper(II) and nickel(II) complexes with oxime-type Schiff base ligands. Chin. J. Inorg. Chem. 2017, 33, 1481–1488. [Google Scholar]
  8. Yu, B.; Sun, Y.X.; Yang, C.J.; Guo, J.Q.; Li, J. Synthesis and crystal structures of an unexpected tetranuclear zinc(II) complex and a benzoquinone compound derived from ZnII- and CdII-promoted reactivity of Schiff base ligands. Z. Anorg. Allg. Chem. 2017, 643, 689–698. [Google Scholar] [CrossRef]
  9. Song, X.Q.; Liu, P.P.; Liu, Y.A.; Zhou, J.J.; Wang, X.L. Two dodecanuclear heterometallic [Zn6Ln6] clusters constructed by a multidentate salicylamide salen-like ligand: Synthesis, structure, luminescence and magnetic properties. Dalton Trans. 2016, 45, 8154–8163. [Google Scholar] [CrossRef]
  10. Chin, T.K.; Endud, S.; Jamil, S.; Budagumpi, S.; Lintang, H.O. Oxidative dimerization of o-aminophenol by heterogeneous mesoporous material modified with biomimetic salen-type copper(II) complex. Catal. Lett. 2013, 143, 282–288. [Google Scholar] [CrossRef]
  11. Yang, X.P.; Schipper, D.; Liao, A.; Stanley, J.M.; Jones, R.A.; Holliday, B.J. Anion dependent self-assembly of luminescent Zn–Ln (Eu and Tb) salen complexes. Polyhedron 2013, 52, 165–169. [Google Scholar] [CrossRef]
  12. Akine, S.; Piao, S.J.; Miyashita, M.; Nabeshima, T. Cage-like tris(salen)-type metallocryptand for cooperative guest recognition. Tetrahedron Lett. 2013, 54, 6541–6544. [Google Scholar] [CrossRef]
  13. Li, X.Y.; Kang, Q.P.; Liu, L.Z.; Ma, J.C.; Dong, W.K. Trinuclear Co(II) and mononuclear Ni(II) salamo-type bisoxime coordination compounds. Crystals 2018, 8, 43. [Google Scholar] [CrossRef]
  14. Wang, F.; Liu, L.Z.; Gao, L.; Dong, W.K. Unusual constructions of two salamo-based copper(II) complexes. Spectrochim. Acta A 2018, 203, 56–64. [Google Scholar] [CrossRef] [PubMed]
  15. Peng, Y.D.; Wang, F.; Gao, L.; Dong, W.K. Structurally characterized dinuclear zinc(II) bis(salamo)-type tetraoxime complex possessing square pyramidal and trigonal bipyramidal geometries. J. Chin. Chem. Soc. 2018, 65, 893–899. [Google Scholar] [CrossRef]
  16. Kang, Q.P.; Li, X.Y.; Zhao, Q.; Ma, J.C.; Dong, W.K. Structurally characterized homotrinuclear salamo-type nickel(II) complexes: Synthesis, solvent effect and fluorescence properties. Appl. Organomet. Chem. 2018, 32, e4379. [Google Scholar] [CrossRef]
  17. Zhang, L.W.; Liu, L.Z.; Wang, F.; Dong, W.K. Unprecedented fluorescent dinuclear CoII and ZnII coordination compounds with a symmetric bis(salamo)-like tetraoxime. Molecules 2018, 23, 1141. [Google Scholar] [CrossRef]
  18. Andruh, M. Oligonuclear complexes as tectons in crystal engineering: Structural diversity and magnetic properties. Chem. Commun. 2007, 25, 2565–2577. [Google Scholar] [CrossRef]
  19. Zhang, L.W.; Li, X.Y.; Kang, Q.P.; Liu, L.Z.; Ma, J.C.; Dong, W.K. Structures and fluorescent and magnetic behaviors of newly synthesized NiII and CuII coordination compounds. Crystals 2018, 8, 173. [Google Scholar] [CrossRef]
  20. Yamashita, A.; Watanabe, A.; Akine, S.; Nabeshima, T.; Nakano, M.; Yamamura, T.; Kajiwara, T. Wheel-shaped ErIIIZnII3 single-molecule magnet: A macrocyclic approach to designing magnetic anisotropy. Angew. Chem. Int. Ed. 2011, 50, 4016–4019. [Google Scholar] [CrossRef]
  21. Song, X.Q.; Wang, C.Y.; Meng, H.H.; Shamshoom, A.A.A.; Liu, W.S. Coordination-driven self-assembled ZnII6-LnIII3 metallocycles based on a salicylamide imine ligand: Synthesis, structure, and selective luminescence enhancement induced by OAc−. Inorg. Chem. 2018, 57, 10873–10880. [Google Scholar] [CrossRef] [PubMed]
  22. Song, X.Q.; Liu, P.P.; Xiao, Z.R.; Li, X.; Liu, Y.A. Four polynuclear complexes a versatile salicylamide salen-like ligand: Synthesis, structural variations and magnetic properties. Inorg. Chim. Acta 2015, 438, 232–244. [Google Scholar] [CrossRef]
  23. Costes, J.P.; Yamaguchi, T.; Kojima, M.; Vendier, L. Experimental evidence for the participation of 5d GdIII orbitals in the magnetic interaction in Ni-Gd complexes. Inorg. Chem. 2009, 48, 5555–5561. [Google Scholar] [CrossRef] [PubMed]
  24. Yamaguchi, T.; Costes, J.P.; Kishima, Y.; Kojima, M.; Sunatsuki, Y.; Bréfuel, N.; Tuchagues, J.P.; Vendier, L.; Wernsdorfer, W. Face-sharing heterotrinuclear M(II)-Ln(III)-M(II) (M = Mn, Fe, Co, Zn; Ln = La, Gd, Tb, Dy) complexes: Synthesis, structures, and magnetic properties. Inorg. Chem. 2010, 49, 9125–9135. [Google Scholar] [CrossRef]
  25. Li, J.; Zhang, H.J.; Chang, J.; Jia, H.R.; Sun, Y.X.; Huang, Y.Q. Solvent-induced unsymmetric Salamo-like trinuclear NiII complexes: Syntheses, crystal structures, fluorescent and magnetic properties. Crystals 2018, 8, 176. [Google Scholar] [CrossRef]
  26. Li, L.H.; Dong, W.K.; Zhang, Y.; Akogun, S.F.; Xu, L. Syntheses, structures and catecholase activities of homo-and hetero-trinuclear cobalt(II) complexes constructed from an acyclic naphthalenediol-based bis(salamo)-type ligand. Appl. Organomet. Chem. 2017, 31, e3818. [Google Scholar] [CrossRef]
  27. Li, X.Y.; Kang, Q.P.; Liu, C.; Zhang, Y.; Dong, W.K. Structurally characterized homo-trinuclear ZnII and hetero-pentanuclear [ZnII4LnIII] complexes constructed from an octadentate bis(Salamo)-based ligand: Hirshfeld surfaces, fluorescence and catalytic properties. New J. Chem. 2019, 43, 4605–4619. [Google Scholar] [CrossRef]
  28. Chen, C.Y.; Zhang, J.W.; Zhang, Y.H.; Yang, Z.H.; Wu, H.L.; Pan, G.L.; Bai, Y.C. Gadolinium(III) and dysprosium(III) complexes with a Schiff base bis(N-salicylidene)-3-oxapentane-1,5-diamine: Synthesis, characterization, antioxidation, and DNA-binding studies. J. Coord. Chem. 2015, 68, 1054–1071. [Google Scholar] [CrossRef]
  29. Wu, H.L.; Wang, H.; Wang, X.L.; Pan, G.L.; Shi, F.R.; Zhang, Y.H.; Bai, Y.C.; Kong, J. V-shaped ligand bis(2-benzimidazolylmethyl)amine containing three copper(II) ternary complexes: Synthesis, structure, DNA binding properties and antioxidant activity. New J. Chem. 2014, 38, 1052–1061. [Google Scholar] [CrossRef]
  30. Zhang, H.; Xu, Y.L.; Wu, H.L.; Aderinto, S.O.; Fan, X.Y. Mono-, bi- and multi-nuclear silver complexes constructed from bis(benzimidazole)-2-oxapropane ligands and methacrylate: Syntheses, crystal structures, DNA-binding properties and antioxidant activities. RSC Adv. 2016, 6, 83697–83708. [Google Scholar] [CrossRef]
  31. Gao, L.; Liu, C.; Wang, F.; Dong, W.K. Tetra-, penta- and hexa-coordinated transition metal complexes constructed from coumarin-containing N2O2 ligand. Crystals 2018, 8, 77. [Google Scholar] [CrossRef]
  32. Chai, L.Q.; Zhang, K.Y.; Tang, L.J.; Zhang, J.Y.; Zhang, H.S. Two mono- and dinuclear Ni(II) complexes constructed from quinazoline-type ligands: Synthesis, X-ray structures, spectroscopic, electrochemical, thermal, and antimicrobial studies. Polyhedron 2017, 130, 100–107. [Google Scholar] [CrossRef]
  33. Chai, L.Q.; Li, Y.X.; Chen, L.C.; Zhang, J.Y.; Huang, J.J. Synthesis, X-ray structure, spectroscopic, electrochemical properties and DFT calculation of a bridged dinuclear copper(II) complex. Inorg. Chim. Acta 2016, 444, 193–201. [Google Scholar] [CrossRef]
  34. Ren, Z.L.; Hao, J.; Hao, P.; Dong, X.Y.; Bai, Y.; Dong, W.K. Synthesis, crystal structure, luminescence and electrochemical properties of a salamo-type trinuclear cobalt(II) complex. Z. Nat. B 2018, 73, 203–210. [Google Scholar] [CrossRef]
  35. Chai, L.Q.; Tang, L.J.; Chen, L.C.; Huang, J.J. Structural, spectral, electrochemical and DFT studies of two mononuclear manganese(II) and zinc(II) complexes. Polyhedron 2017, 122, 228–240. [Google Scholar] [CrossRef]
  36. Chai, L.Q.; Hu, Q.; Zhang, K.Y.; Chen, L.C.; Li, Y.X.; Zhang, H.S. X-ray structures, spectroscopic, electrochemical, thermal, antibacterial, and DFT studies of two nickel(II) and cobalt(III) complexes constructed from a new quinazoline-type ligand. Appl. Organomet. Chem. 2018, 32, e4426. [Google Scholar] [CrossRef]
  37. Chai, L.Q.; Zhou, L.; Zhang, K.Y.; Zhang, H.S. Structural characterizations, spectroscopic, electrochemical properties, and antibacterial activities of copper (II) and cobalt (II) complexes containing imidazole ring. Appl. Organomet. Chem. 2018, 32, e4576. [Google Scholar] [CrossRef]
  38. Nabeshima, T.; Yamamura, M. Cooperative formation and functions of multimetal supramolecular systems. Pure Appl. Chem. 2013, 85, 763–776. [Google Scholar] [CrossRef]
  39. Akine, S.; Hotate, S.; Nabeshima, T.A. Molecular leverage for helicity control and helix inversion. J. Am. Chem. Soc. 2011, 133, 13868–13871. [Google Scholar] [CrossRef]
  40. Akine, S.; Matsumoto, T.; Sairenji, S.; Nabeshima, T. Synthesis of acyclic tetrakis- and pentakis(N2O2) ligands for single-helical heterometallic complexes with a greater number of winding turns. Supramol. Chem. 2011, 23, 106–112. [Google Scholar] [CrossRef]
  41. Zhang, Y.; Liu, L.Z.; Peng, Y.D.; Li, N.; Dong, W.K. Structurally characterized trinuclear nickel(II) and copper(II) salamo type complexes: Syntheses, Hirshfeld analyses and fuorescent properties. Transit. Met. Chem. 2019, 44, 627–639. [Google Scholar] [CrossRef]
  42. Kang, Q.P.; Li, X.Y.; Wang, L.; Zhang, Y.; Dong, W.K. Containing-PMBP N2O2-donors transition metal(II) complexes: Synthesis, crystal structure, Hirshfeld surface analyses and fluorescence properties. Appl. Organomet. Chem. 2019, 33, e5013. [Google Scholar] [CrossRef]
  43. Liu, L.Z.; Yu, M.; Li, X.Y.; Kang, Q.P.; Dong, W.K. Syntheses, structures, Hirshfeld analyses and fluorescent properties of two Ni(II) and Zn(II) complexes constructed from a bis(salamo)-like ligand. Chin. J. Inorg. Chem. 2019, 35, 1283–1294. [Google Scholar]
  44. Kang, Q.P.; Li, X.Y.; Wei, Z.L.; Zhang, Y.; Dong, W.K. Symmetric containing-PMBP N2O2-donors nickel(II) complexes: Syntheses, structures, Hirshfeld analyses and fluorescent properties. Polyhedron 2019, 165, 38–50. [Google Scholar] [CrossRef]
  45. Chai, L.Q.; Mao, K.H.; Zhang, J.Y.; Zhang, K.Y.; Zhang, H.S. Synthesis, X-ray crystal structure, spectroscopic, electrochemical and antimicrobial studies of a new dinuclear cobalt(III) complex. Inorg. Chim. Acta 2017, 457, 34–40. [Google Scholar] [CrossRef]
  46. Jia, H.R.; Chang, J.; Zhang, H.J.; Li, J.; Sun, Y.X. Three polyhydroxyl-bridged defective dicubane tetranuclear MnIII complexes: Synthesis, crystal structures, and spectroscopic properties. Crystals 2018, 8, 272. [Google Scholar] [CrossRef] [Green Version]
  47. Chai, L.Q.; Hu, Q.; Zhang, K.Y.; Zhou, L.; Huang, J.J. Synthesis, structural characterization, spectroscopic, and DFT studies of two pentacoordinated zinc(II) complexes containing quinazoline and 1, 10-phenanthroline as mixed ligands. J. Lumin. 2018, 203, 234–246. [Google Scholar] [CrossRef]
  48. Jia, H.R.; Li, J.; Sun, Y.X.; Guo, J.Q.; Yu, B.; Wen, N.; Xu, L. Two supramolecular cobalt(II) complexes: Syntheses, crystal structures, spectroscopic behaviors, and counter anion effects. Crystals 2017, 7, 247. [Google Scholar]
  49. Zhou, L.; Hu, Q.; Chai, L.Q.; Mao, K.H.; Zhang, H.S. X-ray characterization, spectroscopic, DFT calculations and Hirshfeld surface analysis of two 3-D supramolecular mononuclear zinc(II) and trinuclear copper(II) complexes. Polyhedron 2019, 158, 102–116. [Google Scholar] [CrossRef]
  50. Sun, Y.X.; Zhao, Y.Y.; Li, C.Y.; Yu, B.; Guo, J.Q.; Li, J. Supramolecular cobalt(II) and copper(II) complexes with Schiff base ligand: Syntheses, characterizations and crystal structures. Chin. J. Inorg. Chem. 2016, 32, 913–920. [Google Scholar]
  51. Chai, L.Q.; Tang, L.J.; Zhang, K.Y.; Zhang, J.Y.; Zhang, H.S. Two two-dimensional supramolecular copper(II) and cobalt(III) complexes derived from a new quinazoline-type ligand: Syntheses, structures, and spectral, thermal, electrochemical and antimicrobial activity studies. Appl. Organomet. Chem. 2017, 31, e3786. [Google Scholar] [CrossRef]
  52. Hu, J.H.; Sun, Y.; Qi, J.; Li, Q.; Wei, T.B. A new unsymmetrical azine derivative based on coumarin group as dual-modal sensor for CN− and fluorescent “OFF-ON” for Zn2+. Spectrochim. Acta A 2017, 175, 125–133. [Google Scholar] [CrossRef] [PubMed]
  53. Sun, Y.; Hu, J.H.; Qi, J.; Li, J.B. A highly selective colorimetric and “turn-on” fluorimetric chemosensor for detecting CN− based on unsymmetrical azine derivatives in aqueous media. Spectrochim. Acta A 2016, 167, 101–105. [Google Scholar] [CrossRef] [PubMed]
  54. Liu, L.Z.; Wang, L.; Yu, M.; Zhao, Q.; Zhang, Y.; Sun, Y.X.; Dong, W.K. A highly sensitive and selective fluorescent “off-on-off” relay chemosensor based on a new bis(salamo)-type tetraoxime for detecting Zn2+ and CN−. Spectrochim. Acta A 2019, 222, 117209. [Google Scholar] [CrossRef] [PubMed]
  55. Hao, J.; Li, X.Y.; Zhang, Y.; Dong, W.K. A reversible bis(salamo)-based fluorescence sensor for selective detection of Cd2+ in water-containing systems and food samples. Materials 2018, 11, 523. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  56. Yu, B.; Li, C.Y.; Sun, Y.X.; Jia, H.R.; Guo, J.Q.; Li, J. A new azine derivative colorimetric and fluorescent dual-channel probe for cyanide detection. Spectrochim. Acta A 2017, 184, 249–254. [Google Scholar] [CrossRef] [PubMed]
  57. Liao, S.; Yang, X.P.; Jones, R.A. Self-assembly of luminescent hexanuclear lanthanide salen complexes. Cryst. Growth Des. 2012, 12, 970–974. [Google Scholar] [CrossRef]
  58. Wang, B.; Zang, Z.P.; Wang, H.H.; Dou, W.; Tang, X.L.; Liu, W.S.; Shao, Y.L.; Ma, J.X.; Li, Y.Z.; Zhou, J. Multiple lanthanide helicate clusters and the effects of anions on their configuration. Angew. Chem. 2013, 125, 3844–3847. [Google Scholar] [CrossRef]
  59. Feng, W.X.; Zhang, Y.; Zhang, Z.; Lü, X.Q.; Liu, H.; Shi, G.X.; Zou, D.; Song, J.R.; Fan, D.D.; Wong, W.K.; et al. Anion-induced self-assembly of luminescent and magnetic homoleptic cyclic tetranuclear Ln4(Salen)4 and Ln4(Salen)2 complexes (Ln = Nd, Yb, Er, or Gd). Inorg. Chem. 2012, 51, 11377–11386. [Google Scholar] [CrossRef]
  60. Zhao, Q.; An, X.X.; Liu, L.Z.; Dong, W.K. Syntheses, luminescences and Hirshfeld surfaces analyses of structurally characterized homo-trinuclear ZnII and hetero-pentanuclear ZnII-LnIII (Ln=Eu, Nd) bis(salamo)-like complexes. Inorg. Chim. Acta 2019, 490, 6–15. [Google Scholar] [CrossRef]
  61. Akine, S.; Utsuno, F.; Taniguchi, T.; Nabeshima, T. Dinuclear complexes of the N2O2 oxime chelate ligand with Zinc(II)–Lanthanide(III) as a selective sensitization system for Sm3+. Eur. J. Inorg. Chem. 2010, 20, 3143–3152. [Google Scholar] [CrossRef]
  62. Song, X.Q.; Liu, P.P.; Wang, C.Y.; Liu, Y.A.; Liu, W.S.; Zhang, M. Three sandwich-type zinc(II)–lanthanide(III) clusters: Structures, luminescence and magnetic properties. RSC Adv. 2017, 7, 22692–22698. [Google Scholar] [CrossRef] [Green Version]
  63. Pasatoiu, T.D.; Tiseanu, C.; Madalan, A.M.; Jurca, B.; Duhayon, C.; Sutter, J.P.; Andruh, M. Study of the luminescent and magnetic properties of a series of heterodinuclear [Zn(II)Ln(III)] complexes. Inorg. Chem. 2011, 50, 5879–5889. [Google Scholar] [CrossRef] [PubMed]
  64. Pasatoiu, T.D.; Madalan, A.M.; Kumke, M.U.; Tiseanu, C.; Andruh, M. Study of the luminescent and magnetic properties of a series of heterodinuclear [ZnIILnIII] complexes. Inorg. Chem. 2010, 49, 2310–2315. [Google Scholar] [CrossRef] [PubMed]
  65. Dong, W.K.; Ma, J.C.; Zhu, L.C.; Sun, Y.X.; Akogun, S.F.; Zhang, Y. A series of heteromultinuclear Zinc(II)-Lanthanide(III) complexes based on 3-MeOsalamo: Syntheses, structural characterizations, and luminescent properties. Cryst. Growth Des. 2016, 16, 6903–6914. [Google Scholar] [CrossRef]
  66. An, X.X.; Zhao, Q.; Mu, H.R.; Dong, W.K. A new half-salamo-based homo-trinuclear nickel(II) complex: Crystal structure, Hirshfeld surface analysis, and fluorescence properties. Crystals 2019, 9, 101. [Google Scholar] [CrossRef] [Green Version]
  67. Peng, Y.D.; Li, X.Y.; Kang, Q.P.; An, G.X.; Zhang, Y.; Dong, W.K. Synthesis and fluorescence properties of asymmetrical Salamo-type tetranuclear zinc(II) complex. Crystals 2018, 8, 107. [Google Scholar] [CrossRef] [Green Version]
  68. Hu, J.H.; Li, J.B.; Qi, J.; Sun, Y. Acylhydrazone based fluorescent chemosensor for zinc in aqueous solution with high selectivity and sensitivity. Sens. Actuators B 2015, 208, 581–587. [Google Scholar] [CrossRef]
  69. Hao, J.; Li, X.Y.; Wang, L.; Zhang, Y.; Dong, W.K. Luminescent and electrochemical properties of four novel butterfly-shaped hetero-pentanuclear [Zn4Ln] complexes constructed from a bis(salamo)-type ligand. Spectrochim. Acta A 2018, 204, 388–402. [Google Scholar] [CrossRef]
  70. Dong, X.Y.; Kang, Q.P.; Li, X.Y.; Ma, J.C.; Dong, W.K. Structurally characterized solvent-induced homotrinuclear cobalt(II) N2O2-donor bisoxime-type complexes. Crystals 2018, 8, 139. [Google Scholar] [CrossRef] [Green Version]
  71. Brubaker, C.D.; Frecker, T.M.; McBride, J.R.; Reid, K.R.; Jennings, G.K.; Rosenthal, S.J.; Adams, D.E. Incorporation of fluorescent quantum dots for 3D printing and additive manufacturing applications. J. Mater. Chem. C 2018, 6, 7584–7593. [Google Scholar] [CrossRef]
  72. Kim, B.H.; Onses, M.S.; Lim, J.B.; Nam, S.; Oh, N.; Kim, H.; Yu, K.J.; Lee, J.W.; Kim, J.H.; Kang, S.K.; et al. High-resolution patterns of quantum dots formed by electrohydrodynamic jet printing for light-emitting diodes. Nano Lett. 2015, 15, 969–973. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  73. Kumar, P.; Singh, S.; Gupta, B.K. Future prospects of luminescent nanomaterial based security inks: From synthesis to anti-counterfeiting applications. Nanoscale 2016, 8, 14297–14340. [Google Scholar] [CrossRef] [PubMed]
Crystals 09 00602 sch001 550
Scheme 1. Synthetic routes to H2L and its [ZnII2–SmIII2] complex.
Scheme 1. Synthetic routes to H2L and its [ZnII2–SmIII2] complex.
Crystals 09 00602 sch001
Crystals 09 00602 g001 550
Figure 1. Comparison of the simulated and experimental powder X-ray diffraction (PXRD) patterns of the [ZnII2–SmIII2] complex.
Figure 1. Comparison of the simulated and experimental powder X-ray diffraction (PXRD) patterns of the [ZnII2–SmIII2] complex.
Crystals 09 00602 g001
Crystals 09 00602 g002 550
Figure 2. The UV–Vis spectra of H2L and the [ZnII2–SmIII2] complex.
Figure 2. The UV–Vis spectra of H2L and the [ZnII2–SmIII2] complex.
Crystals 09 00602 g002
Crystals 09 00602 g003 550
Figure 3. (a) Crystal structure diagram of the [ZnII2–SmIII2] complex (30% probability displacement ellipsoids, a hydrogen atom, and two free methanol molecules are omitted for clarity), (b) Coordination pattern diagram of ZnII/SmIII ions and 4,4′-bipyridine.
Figure 3. (a) Crystal structure diagram of the [ZnII2–SmIII2] complex (30% probability displacement ellipsoids, a hydrogen atom, and two free methanol molecules are omitted for clarity), (b) Coordination pattern diagram of ZnII/SmIII ions and 4,4′-bipyridine.
Crystals 09 00602 g003
Crystals 09 00602 g004 550
Figure 4. (a) Intramolecular hydrogen-bonding interactions of the [ZnII2–SmIII2] complex, (b) two-dimensional (2-D) supramolecular structure of the [ZnII2–SmIII2] complex, (c) three-dimensional (3-D) center perspective structure of the [ZnII2–SmIII2] complex.
Figure 4. (a) Intramolecular hydrogen-bonding interactions of the [ZnII2–SmIII2] complex, (b) two-dimensional (2-D) supramolecular structure of the [ZnII2–SmIII2] complex, (c) three-dimensional (3-D) center perspective structure of the [ZnII2–SmIII2] complex.
Crystals 09 00602 g004
Crystals 09 00602 g005 550
Figure 5. The solid fluorescence spectrum of the [ZnII2–SmIII2] complex.
Figure 5. The solid fluorescence spectrum of the [ZnII2–SmIII2] complex.
Crystals 09 00602 g005
Crystals 09 00602 g006 550
Figure 6. (a) Fluorescence spectra of H2L and the [ZnII2–SmIII2] complex in ethanol solution (1.0 × 10−5 M), (b) Fluorescence spectra of H2L changes after the addition of Zn(OAc)2·2H2O, (c) Fluorescence spectra of the changes in [L–Zn2+] upon addition of Sm(NO3)3·6H2O.
Figure 6. (a) Fluorescence spectra of H2L and the [ZnII2–SmIII2] complex in ethanol solution (1.0 × 10−5 M), (b) Fluorescence spectra of H2L changes after the addition of Zn(OAc)2·2H2O, (c) Fluorescence spectra of the changes in [L–Zn2+] upon addition of Sm(NO3)3·6H2O.
Crystals 09 00602 g006
Crystals 09 00602 g007 550
Figure 7. The Fluorescence lifetime of H2L and the [ZnII2–SmIII2] complex.
Figure 7. The Fluorescence lifetime of H2L and the [ZnII2–SmIII2] complex.
Crystals 09 00602 g007
Crystals 09 00602 g008 550
Figure 8. Color contrast of H2L and its [ZnII2–SmIII2] complex in ethanol solution under natural light (a), Under 365 nm UV light (b), Fluorescent imaging with H2L labeling (c), Fluorescent imaging of the [ZnII2–SmIII2] complex (d).
Figure 8. Color contrast of H2L and its [ZnII2–SmIII2] complex in ethanol solution under natural light (a), Under 365 nm UV light (b), Fluorescent imaging with H2L labeling (c), Fluorescent imaging of the [ZnII2–SmIII2] complex (d).
Crystals 09 00602 g008
Crystals 09 00602 g009 550
Figure 9. Surface plots of selected molecular orbitals of H2L and the [ZnII2–SmIII2] complex.
Figure 9. Surface plots of selected molecular orbitals of H2L and the [ZnII2–SmIII2] complex.
Crystals 09 00602 g009
Table
Table 1. Crystal data and refinement parameters for the [ZnII2–SmIII2] complex.
Table 1. Crystal data and refinement parameters for the [ZnII2–SmIII2] complex.
CompoundThe [ZnII2–SmIII2] Complex
FormulaC50H56N12O32Sm2Zn2
Formula weight1768.50
Temperature (K)273.15
Wavelength (Å)0.71073
Crystal systemmonoclinic
Space groupC 2/c
a (Å)36.6271(14)
b (Å)8.8968(3)
c (Å)21.4485(8)
α (°)90.00
β (°)112.6940(10)
γ (°)90.00
V (Å3)6448.2(4)
Z4
Dcalc (g∙cm–3)2.631
µ (mm–1)3.325
F (000)3520.0
Crystal size (mm)0.15 × 0.11× 0.09
θ Range (°)2.5–26.0
Index ranges–44 ≤ h ≤ 44,
–10 ≤ k ≤10,
–26 ≤ l ≤ 26
Reflections collected25,740
Independent reflections6310
Rint0.0291
Completeness to θ99.7 % (θ = 26.0)
Data/restraints/parameters6310/100/473
GOF1.036
R [I > 2σ(I)]R1 = 0.0333, wR2 = 0.0747
Largest differences peak and hole (e Å−3)0.92/−0.64
R1 = Σ‖Fo| − |Fc‖/Σ|Fo|, wR2 = [Σw(Fo2 − Fc2)2/Σw(Fo2)2]1/2, w = [σ2(Fo2) + ( 0.0289P)2+31.3296P]−1, where P = (Fo2 + 2Fc2)/3, GOF = [Σw(Fo2 − Fc2)2/nobs − nparam)]1/2.
Table
Table 2. Main infrared data (cm−1) for H2L and the [ZnII2–SmIII2] complex.
Table 2. Main infrared data (cm−1) for H2L and the [ZnII2–SmIII2] complex.
Compoundν(O-H)ν(C=N)ν(Ar–O)ν(C=C)
H2L3427161312501468
The [ZnII2–SmIII2] complex3400160712161461
Table
Table 3. Hydrogen-bonding interactions (Å, °) of the [ZnII2–SmIII2] complex.
Table 3. Hydrogen-bonding interactions (Å, °) of the [ZnII2–SmIII2] complex.
D–H···Ad(D–H)d(H···A)d(D···A)∠D–H···ASymmetry Code
C20–H9B···O130.932.382.996(6)123
C24–H24···O40.932.493.298(6)146
C12–H12···O90.930.933.291(6)1671/2 − x, −1/2 − y, 1/2 − z
C23–H23···O11
C23–H23···O14
C24–H24···O11		0.93
0.93
0.93		2.59
2.53
2.47		3.162(6)
3.354(5)
3.112(5)		120
148
127		x, 1 − y, −1/2 + z
x, 1 − y, −1/2 + z
x, 1 − y, −1/2 + z

Share and Cite

MDPI and ACS Style

An, X.-X.; Liu, C.; Chen, Z.-Z.; Xie, K.-F.; Zhang, Y. Fluorescence Properties and Density Functional Theory Calculation of a Structurally Characterized Heterotetranuclear [ZnII2–SmIII2] 4,4′-Bipy-Salamo-Constructed Complex. Crystals 2019, 9, 602. https://doi.org/10.3390/cryst9110602

AMA Style

An X-X, Liu C, Chen Z-Z, Xie K-F, Zhang Y. Fluorescence Properties and Density Functional Theory Calculation of a Structurally Characterized Heterotetranuclear [ZnII2–SmIII2] 4,4′-Bipy-Salamo-Constructed Complex. Crystals. 2019; 9(11):602. https://doi.org/10.3390/cryst9110602

Chicago/Turabian Style

An, Xiao-Xin, Chang Liu, Zhuang-Zhuang Chen, Ke-Feng Xie, and Yang Zhang. 2019. "Fluorescence Properties and Density Functional Theory Calculation of a Structurally Characterized Heterotetranuclear [ZnII2–SmIII2] 4,4′-Bipy-Salamo-Constructed Complex" Crystals 9, no. 11: 602. https://doi.org/10.3390/cryst9110602

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop