Synthesis, Structures, and Magnetism of Four One-Dimensional Complexes Using [Ni(CN)4]2− and Macrocyclic Metal Complexes

Four one-dimensional complexes, denoted as [NiL1][Ni(CN)4] (1), [CuL1][Ni(CN)4] (2), [NiL2][Ni(CN)4]·2H2O (3), and [CuL2][Ni(CN)4]·2H2O (4) (L1 = 1,8-dimethyl-1,3,6,8,10,13-hexaaza-cyclotetradecane; L2 = 1,8-dipropyl-1,3,6,8,10,13-hexaazacyclotetradecane) were synthesized by reacting nickel/copper macrocyclic complexes with K2[Ni(CN)4]. Subsequently, the synthesized complexes were characterized using elemental analysis, infrared spectroscopy analysis, thermogravimetric analysis, and X-ray powder diffraction. Single-crystal structure analysis revealed that the Ni(II)/Cu(II) atoms were coordinated by two nitrogen atoms from [Ni(CN)4]2− with four nitrogen atoms from a macrocyclic ligand, forming a six-coordinated octahedral coordination geometry. Nickel/copper macrocyclic complexes were bridged by [Ni(CN)4]2− to construct one-dimensional chain structures in 1–4. The characterization results showed that the four complexes obeyed the Curie–Weiss law with a weak antiferromagnetic exchange coupling.


XRD and TG
X-ray powder diffraction measurements for 1-4 ( Figure 3) showed that the pe the measured patterns for both complexes closely matched those in the simulated pa generated from single-crystal diffraction data, indicating that single phases were fo     The decomposition of the macrocyclic structure was observed after the further h ing of the macrocyclic ligand. The TGA curve for 2 showed the first weight loss from ro temperature to 523 K, and the observed weight loss of 22.8% was related to the releas four CN − (calcd 22.7%). Then, the macrocyclic structure began to decompose after the m rocyclic ligand was further heated.
The TGA curve for complex 3 revealed that a weight loss of approximately 27 occurred from room temperature to 630K, which was attributed to the release of adsor water from the air (2.3%), two lattice water molecules (calcd 6.5%), and four CN − (ca 18.6%). The weight loss was attributed to the release of structural water molecules a four CN − . The TGA curve of complex 4 was similar to that of complex 3, which revea that an initial weight loss of 25.3% (calcd 25.5%) occurred from room temperature to K, corresponding to the release of structural water molecules and four CN − .

Magnetism
Magnetic susceptibility measurements were performed to investigate the magn behaviors of complexes 1-4 at 1000 G within the temperature range of 2-300 K. Plot χM vs. T and µeff/µB vs. T of the complexes within the temperature range of 2-300 K shown in Figure 5. Complexes 1 and 3 exhibited similar magnetic properties, and th µeff/µB values within the temperature range of 7-300 K were close to the theoretical va expected for two unpaired d electrons in Ni(II) ions. In addition, complexes 2 and 4 hibited similar magnetic properties, and their µeff/µB values within the temperature ra of 7-300 K were close to the theoretical value expected for an unpaired d electron in Cu ions. The decomposition of the macrocyclic structure was observed after the further heating of the macrocyclic ligand. The TGA curve for 2 showed the first weight loss from room temperature to 523 K, and the observed weight loss of 22.8% was related to the release of four CN − (calcd 22.7%). Then, the macrocyclic structure began to decompose after the macrocyclic ligand was further heated.
The TGA curve for complex 3 revealed that a weight loss of approximately 27.2% occurred from room temperature to 630K, which was attributed to the release of adsorbed water from the air (2.3%), two lattice water molecules (calcd 6.5%), and four CN − (calcd 18.6%). The weight loss was attributed to the release of structural water molecules and four CN − . The TGA curve of complex 4 was similar to that of complex 3, which revealed that an initial weight loss of 25.3% (calcd 25.5%) occurred from room temperature to 496 K, corresponding to the release of structural water molecules and four CN − .

Magnetism
Magnetic susceptibility measurements were performed to investigate the magnetic behaviors of complexes 1-4 at 1000 G within the temperature range of 2-300 K. Plots of χ M vs. T and µ eff /µ B vs. T of the complexes within the temperature range of 2-300 K are shown in Figure 5. Complexes 1 and 3 exhibited similar magnetic properties, and their µ eff /µ B values within the temperature range of 7-300 K were close to the theoretical value expected for two unpaired d electrons in Ni(II) ions. In addition, complexes 2 and 4 exhibited similar magnetic properties, and their µ eff /µ B values within the temperature range of 7-300 K were close to the theoretical value expected for an unpaired d electron in Cu(II) ions.

Materials and Methods
The Ni(II) and Cu(II) macrocycle complexes were prepared following the previous report procedure [29]. All of the chemicals used in this work were commercially available and were used without further purification. Elemental analyses were carried out using an Elementar Micro Cube elemental analyzer. Infrared spectra were recorded in the 4000−400 cm −1 region using KBr pellets and a Bruker EQUINOX 55 spectrometer (Bruker, Germany). Thermogravimetric analyses were performed using a Netzsch STA 449F3 instrument (Netzsch, Germany) in flowing air at a heating rate of 10 °C·min −1 . X-ray powder diffraction data were recorded using a Bruker D8 ADVANCE X-ray powder diffractometer (Cu Kα radiation, λ = 1.5418 Å, Bruker, Germany). Magnetic susceptibility measurements were conducted to determine the magnetic behaviors of both complexes at 1000 G in a temperature range of 2-300 K.

Materials and Methods
The Ni(II) and Cu(II) macrocycle complexes were prepared following the previous report procedure [29]. All of the chemicals used in this work were commercially available and were used without further purification. Elemental analyses were carried out using an Elementar Micro Cube elemental analyzer. Infrared spectra were recorded in the 4000−400 cm −1 region using KBr pellets and a Bruker EQUINOX 55 spectrometer (Bruker, Germany). Thermogravimetric analyses were performed using a Netzsch STA 449F3 instrument (Netzsch, Germany) in flowing air at a heating rate of 10 • C·min −1 . X-ray powder diffraction data were recorded using a Bruker D8 ADVANCE X-ray powder diffractometer (Cu Kα radiation, λ = 1.5418 Å, Bruker, Germany). Magnetic susceptibility measurements were conducted to determine the magnetic behaviors of both complexes at 1000 G in a temperature range of 2-300 K. Crystal Structure Determination. Single-crystal data for 1-4 were collected using a Bruker Smart Apex II diffractometer (Bruker, Germany) with Mo-Kα radiation (λ = 0.71073 Å). All empirical absorption corrections were applied using the SADABS program [30]. All structures were solved using direct methods, which yielded the positions of all nonhydrogen atoms. The positions were first refined isotropically, then anisotropically. All the hydrogen atoms of the ligands were placed in calculated positions with fixed isotropic thermal parameters and included in the structure factor calculations in the final stage of full-matrix least-squares refinement. All calculations were performed using the SHELXTL 5.1 software package [31]. For complexes 3 and 4, the hydrogen atoms bonded to oxygen were introduced at idealized positions and refined as riders with isotropic displacement parameters assigned 1.2 times the U eq value of the corresponding bonding partner. Selected bond lengths and angles are listed in Table 1. The crystallographic data of 1-4 are summarized in Table 2.

Conclusions
In this work, four one-dimensional linear chains were successfully obtained between the reactions of macrocyclic nickel/copper complexes and [Ni(CN) 4 ] 2− . All complexes exhibited one-dimensional linear chain structures, which were formed by bridging [NiL] 2+ /[CuL] 2+ with [Ni(CN) 4 ] 2− moieties. The magnetic susceptibilities revealed Curie-Weiss behavior for complexes 1-4 and the existence of weak antiferromagnetic exchange coupling.