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The proto-alkaloid synephrine {SYN; systematic name: 4-[1-hydroxy-2-(methylamino)ethyl]phenol}, C9H13NO2, is found to crystallize as a neutral molecule in the racemate and as a zwitterion in the pure enantiomer, in which the phenolic H atom has been transferred to the amino group. In the racemate crystal, an enantiomeric pair on an inversion centre is weakly linked by alcoholic O—H and N—H groups into an R22(10) ring. The trigonal pyramidal amino group is also linked to the phenolic and alcoholic groups to form a C(6) chain. In the enantiopure crystal, the deprotonated phenolic O atom is involved in trifurcated hydrogen bonding to two quaternary ammonium groups and an alcoholic O—H group to form a fused R24(11) ring and a C(7) chain. From the results of the crystal structure analysis, thermal analyses and DFT calculations validated from FT–IR spectra, a different tautomer was found in the racemic molecule (RS-SYN) versus the enantiopure molecule (R-SYN).
Keywords: proto-alkaloid; zwitterion; synephrine; crystal structure; HOMO–LUMO energy gap; IR spectra; thermal analysis.
Supporting information
 | Crystallographic Information File (CIF) https://doi.org/10.1107/S2053229618014419/qf3019sup1.cif |
 | Structure factor file (CIF format) https://doi.org/10.1107/S2053229618014419/qf3019RS-SYNsup2.hkl |
| Structure factor file (CIF format) https://doi.org/10.1107/S2053229618014419/qf3019R-SYNsup3.hkl |
 | Chemical Markup Language (CML) file https://doi.org/10.1107/S2053229618014419/qf3019R-SYNsup4.cml |
CCDC references: 1872931; 1872930
Computing details top
For both structures, data collection: CrystalClear-SM Expert (Rigaku, 2015); cell refinement: CrystalClear-SM Expert (Rigaku, 2015); data reduction: SORTAV (Blessing, 1995) and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL2017 (Sheldrick, 2015); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and Mercury (Macrae et al., 2008); software used to prepare material for publication: PLATON (Spek, 2009), WinGX (Farrugia, 2012) and publCIF (Westrip, 2010).
4-[1-Hydroxy-2-(methylamino)ethyl]phenol (RS-SYN) top
Crystal data top
| C9H13NO2 | F(000) = 360 |
| Mr = 167.2 | Dx = 1.287 Mg m−3 |
| Monoclinic, P21/n | Cu Kα radiation, λ = 1.54178 Å |
| Hall symbol: -P 2yn | Cell parameters from 653 reflections |
| a = 8.768 (3) Å | θ = 25.5–68° |
| b = 11.935 (4) Å | µ = 0.74 mm−1 |
| c = 9.001 (3) Å | T = 100 K |
| β = 113.623 (9)° | Prism, colorless |
| V = 863.0 (5) Å3 | 0.4 × 0.3 × 0.2 mm |
| Z = 4 |
Data collection top
| Rigaku XtaLAB P200 diffractometer | 1546 independent reflections |
| Radiation source: sealed x-ray tube | 1107 reflections with I > 2σ(I) |
| Graphite monochromator | Rint = 0.072 |
| Detector resolution: 5.81 pixels mm-1 | θmax = 68.3°, θmin = 7.0° |
| phi or ω oscillation scans | h = −10→10 |
| Absorption correction: multi-scan (REQAB; Rigaku, 1998) | k = −14→14 |
| Tmin = 0.74, Tmax = 0.86 | l = −10→10 |
| 4832 measured reflections |
Refinement top
| Refinement on F2 | Primary atom site location: structure-invariant direct methods |
| Least-squares matrix: full | Secondary atom site location: difference Fourier map |
| R[F2 > 2σ(F2)] = 0.049 | Hydrogen site location: mixed |
| wR(F2) = 0.131 | H atoms treated by a mixture of independent and constrained refinement |
| S = 0.95 | w = 1/[σ2(Fo2) + (0.0795P)2] where P = (Fo2 + 2Fc2)/3 |
| 1546 reflections | (Δ/σ)max < 0.001 |
| 119 parameters | Δρmax = 0.41 e Å−3 |
| 0 restraints | Δρmin = −0.2 e Å−3 |
| 0 constraints |
Special details top
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
| x | y | z | Uiso*/Ueq | ||
| O1 | 0.19178 (18) | 0.73325 (13) | 1.16284 (17) | 0.0282 (4) | |
| H1O | 0.203997 | 0.673758 | 1.216264 | 0.042* | |
| O2 | 0.48132 (18) | 0.59805 (13) | 0.64037 (16) | 0.0258 (4) | |
| N1 | 0.2175 (2) | 0.55872 (16) | 0.34169 (18) | 0.0255 (4) | |
| C1 | 0.2981 (2) | 0.68056 (17) | 0.7561 (2) | 0.0220 (5) | |
| C2 | 0.2115 (3) | 0.77427 (18) | 0.7695 (2) | 0.0256 (5) | |
| H2 | 0.176651 | 0.828257 | 0.68487 | 0.031* | |
| C3 | 0.1745 (3) | 0.79101 (18) | 0.9042 (2) | 0.0267 (5) | |
| H3 | 0.113278 | 0.855362 | 0.909881 | 0.032* | |
| C4 | 0.2268 (2) | 0.71378 (18) | 1.0312 (2) | 0.0232 (5) | |
| C5 | 0.3152 (2) | 0.61982 (18) | 1.0196 (2) | 0.0246 (5) | |
| H5 | 0.352336 | 0.566588 | 1.105246 | 0.03* | |
| C6 | 0.3494 (2) | 0.60360 (18) | 0.8833 (2) | 0.0249 (5) | |
| H6 | 0.408986 | 0.538688 | 0.876586 | 0.03* | |
| C7 | 0.3288 (2) | 0.65820 (17) | 0.6044 (2) | 0.0230 (5) | |
| H7 | 0.333437 | 0.73109 | 0.551555 | 0.028* | |
| C8 | 0.1883 (2) | 0.58744 (19) | 0.4872 (2) | 0.0256 (5) | |
| H8A | 0.178222 | 0.517709 | 0.542175 | 0.031* | |
| H8B | 0.082222 | 0.629101 | 0.45466 | 0.031* | |
| C9 | 0.0896 (3) | 0.4819 (2) | 0.2361 (2) | 0.0327 (5) | |
| H9A | 0.083461 | 0.416044 | 0.2986 | 0.049* | |
| H9B | 0.118195 | 0.458184 | 0.146243 | 0.049* | |
| H9C | −0.018466 | 0.520003 | 0.192977 | 0.049* | |
| H2O | 0.562 (4) | 0.645 (3) | 0.662 (4) | 0.054 (9)* | |
| H1N | 0.314 (3) | 0.523 (2) | 0.377 (3) | 0.028 (6)* |
Atomic displacement parameters (Å2) top
| U11 | U22 | U33 | U12 | U13 | U23 | |
| O1 | 0.0360 (8) | 0.0323 (9) | 0.0218 (7) | 0.0076 (7) | 0.0172 (6) | 0.0022 (6) |
| O2 | 0.0247 (8) | 0.0304 (9) | 0.0240 (7) | 0.0004 (7) | 0.0113 (6) | −0.0013 (6) |
| N1 | 0.0248 (9) | 0.0349 (11) | 0.0159 (8) | 0.0027 (8) | 0.0072 (7) | −0.0012 (7) |
| C1 | 0.0185 (9) | 0.0289 (12) | 0.0175 (9) | −0.0012 (8) | 0.0062 (7) | −0.0024 (8) |
| C2 | 0.0284 (11) | 0.0274 (12) | 0.0219 (10) | 0.0037 (9) | 0.0109 (8) | 0.0036 (8) |
| C3 | 0.0300 (11) | 0.0262 (11) | 0.0260 (10) | 0.0048 (9) | 0.0132 (9) | 0.0000 (8) |
| C4 | 0.0218 (10) | 0.0313 (12) | 0.0179 (10) | −0.0002 (9) | 0.0094 (8) | −0.0046 (8) |
| C5 | 0.0242 (10) | 0.0307 (12) | 0.0188 (9) | 0.0047 (9) | 0.0084 (8) | 0.0027 (8) |
| C6 | 0.0256 (10) | 0.0280 (11) | 0.0210 (10) | 0.0045 (8) | 0.0091 (8) | −0.0016 (8) |
| C7 | 0.0252 (10) | 0.0257 (11) | 0.0187 (9) | 0.0030 (8) | 0.0093 (8) | 0.0025 (8) |
| C8 | 0.0267 (10) | 0.0338 (12) | 0.0177 (9) | 0.0005 (9) | 0.0103 (8) | 0.0010 (8) |
| C9 | 0.0346 (11) | 0.0421 (14) | 0.0197 (9) | −0.0051 (10) | 0.0090 (8) | −0.0021 (9) |
Geometric parameters (Å, º) top
| O1—C4 | 1.358 (2) | C3—H3 | 0.95 |
| O1—H1O | 0.84 | C4—C5 | 1.391 (3) |
| O2—C7 | 1.436 (2) | C5—C6 | 1.388 (3) |
| O2—H2O | 0.86 (4) | C5—H5 | 0.95 |
| N1—C9 | 1.465 (3) | C6—H6 | 0.95 |
| N1—C8 | 1.472 (2) | C7—C8 | 1.517 (3) |
| N1—H1N | 0.88 (3) | C7—H7 | 1 |
| C1—C2 | 1.384 (3) | C8—H8A | 0.99 |
| C1—C6 | 1.394 (3) | C8—H8B | 0.99 |
| C1—C7 | 1.518 (3) | C9—H9A | 0.98 |
| C2—C3 | 1.389 (3) | C9—H9B | 0.98 |
| C2—H2 | 0.95 | C9—H9C | 0.98 |
| C3—C4 | 1.395 (3) | ||
| C4—O1—H1O | 109.5 | C5—C6—H6 | 119.3 |
| C7—O2—H2O | 110 (2) | C1—C6—H6 | 119.3 |
| C8—N1—C9 | 111.24 (16) | O2—C7—C8 | 107.58 (16) |
| C9—N1—H1N | 107.8 (16) | O2—C7—C1 | 111.69 (15) |
| C8—N1—H1N | 105.9 (15) | C8—C7—C1 | 109.64 (16) |
| C2—C1—C6 | 117.94 (17) | O2—C7—H7 | 109.3 |
| C2—C1—C7 | 121.44 (17) | C8—C7—H7 | 109.3 |
| C6—C1—C7 | 120.54 (18) | C1—C7—H7 | 109.3 |
| C1—C2—C3 | 121.35 (19) | N1—C8—C7 | 111.48 (16) |
| C1—C2—H2 | 119.3 | N1—C8—H8A | 109.3 |
| C3—C2—H2 | 119.3 | C7—C8—H8A | 109.3 |
| C2—C3—C4 | 120.31 (19) | N1—C8—H8B | 109.3 |
| C2—C3—H3 | 119.8 | C7—C8—H8B | 109.3 |
| C4—C3—H3 | 119.8 | H8A—C8—H8B | 108 |
| O1—C4—C5 | 122.06 (18) | N1—C9—H9A | 109.5 |
| O1—C4—C3 | 119.13 (18) | N1—C9—H9B | 109.5 |
| C5—C4—C3 | 118.81 (18) | H9A—C9—H9B | 109.5 |
| C6—C5—C4 | 120.17 (18) | N1—C9—H9C | 109.5 |
| C6—C5—H5 | 119.9 | H9A—C9—H9C | 109.5 |
| C4—C5—H5 | 119.9 | H9B—C9—H9C | 109.5 |
| C5—C6—C1 | 121.41 (19) | ||
| C6—C1—C2—C3 | −0.8 (3) | C7—C1—C6—C5 | −176.76 (18) |
| C7—C1—C2—C3 | 175.90 (19) | C2—C1—C7—O2 | 149.85 (18) |
| C1—C2—C3—C4 | 1.1 (3) | O2—C7—C1—C6 | −33.5 (3) |
| C2—C3—C4—O1 | 178.73 (18) | C2—C1—C7—C8 | −91.0 (2) |
| C2—C3—C4—C5 | −0.4 (3) | C6—C1—C7—C8 | 85.6 (2) |
| O1—C4—C5—C6 | −179.51 (17) | C9—N1—C8—C7 | 174.72 (17) |
| C3—C4—C5—C6 | −0.4 (3) | O2—C7—C8—N1 | −55.4 (2) |
| C4—C5—C6—C1 | 0.6 (3) | C1—C7—C8—N1 | −177.02 (16) |
| C2—C1—C6—C5 | 0.0 (3) |
Hydrogen-bond geometry (Å, º) top
| D—H···A | D—H | H···A | D···A | D—H···A |
| O1—H1O···N1i | 0.84 | 1.75 | 2.587 (2) | 173 |
| O2—H2O···O1ii | 0.86 (4) | 1.84 (4) | 2.683 (2) | 164 (3) |
| N1—H1N···O2iii | 0.88 (3) | 2.36 (3) | 3.188 (2) | 156 (2) |
| Symmetry codes: (i) x, y, z+1; (ii) x+1/2, −y+3/2, z−1/2; (iii) −x+1, −y+1, −z+1. |
4-[1-Hydroxy-2-(methylamino)ethyl]phenol (R-SYN) top
Crystal data top
| C9H13NO2 | F(000) = 360 |
| Mr = 167.2 | Dx = 1.265 Mg m−3 |
| Orthorhombic, P212121 | Cu Kα radiation, λ = 1.54178 Å |
| Hall symbol: P 2ac 2ab | Cell parameters from 1029 reflections |
| a = 6.5581 (15) Å | θ = 25.7–68.2° |
| b = 7.8144 (18) Å | µ = 0.73 mm−1 |
| c = 17.137 (5) Å | T = 100 K |
| V = 878.2 (4) Å3 | Plate, colorless |
| Z = 4 | 0.4 × 0.4 × 0.2 mm |
Data collection top
| Rigaku XtaLAB P200 diffractometer | 1586 independent reflections |
| Radiation source: sealed x-ray tube | 1504 reflections with I > 2σ(I) |
| Graphite monochromator | Rint = 0.047 |
| Detector resolution: 5.81 pixels mm-1 | θmax = 68.2°, θmin = 7.2° |
| phi or ω oscillation scans | h = −7→7 |
| Absorption correction: multi-scan (REQAB; Rigaku, 1998) | k = −9→9 |
| Tmin = 0.74, Tmax = 0.88 | l = −20→18 |
| 7138 measured reflections |
Refinement top
| Refinement on F2 | Secondary atom site location: difference Fourier map |
| Least-squares matrix: full | Hydrogen site location: difference Fourier map |
| R[F2 > 2σ(F2)] = 0.028 | H atoms treated by a mixture of independent and constrained refinement |
| wR(F2) = 0.098 | w = 1/[σ2(Fo2) + (0.0659P)2] where P = (Fo2 + 2Fc2)/3 |
| S = 1.17 | (Δ/σ)max < 0.001 |
| 1586 reflections | Δρmax = 0.24 e Å−3 |
| 122 parameters | Δρmin = −0.20 e Å−3 |
| 0 restraints | Absolute structure: Flack x determined using 590 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013) |
| 0 constraints | Absolute structure parameter: −0.06 (10) |
| Primary atom site location: structure-invariant direct methods |
Special details top
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
| x | y | z | Uiso*/Ueq | ||
| C1 | 0.3094 (3) | 0.4999 (2) | 0.20752 (10) | 0.0194 (4) | |
| C2 | 0.3508 (3) | 0.4273 (3) | 0.28024 (12) | 0.0228 (4) | |
| H2 | 0.433068 | 0.327445 | 0.28316 | 0.027* | |
| C3 | 0.2739 (3) | 0.4983 (2) | 0.34833 (11) | 0.0222 (4) | |
| H3 | 0.302665 | 0.445235 | 0.396965 | 0.027* | |
| C4 | 0.1541 (3) | 0.6474 (2) | 0.34669 (11) | 0.0198 (4) | |
| C5 | 0.1139 (3) | 0.7205 (3) | 0.27349 (12) | 0.0227 (5) | |
| H5 | 0.034331 | 0.821861 | 0.27039 | 0.027* | |
| C6 | 0.1885 (3) | 0.6470 (3) | 0.20571 (11) | 0.0220 (4) | |
| H6 | 0.156654 | 0.697832 | 0.156847 | 0.026* | |
| C7 | 0.3849 (3) | 0.4194 (3) | 0.13296 (11) | 0.0212 (4) | |
| H7 | 0.428814 | 0.299104 | 0.143749 | 0.025* | |
| C8 | 0.5630 (3) | 0.5188 (2) | 0.09937 (11) | 0.0210 (5) | |
| H8A | 0.518637 | 0.636498 | 0.086467 | 0.025* | |
| H8B | 0.673172 | 0.526414 | 0.138721 | 0.025* | |
| C9 | 0.7764 (3) | 0.5442 (3) | −0.01937 (12) | 0.0289 (5) | |
| H9A | 0.900282 | 0.570073 | 0.010358 | 0.043* | |
| H9B | 0.704806 | 0.650957 | −0.031647 | 0.043* | |
| H9C | 0.813238 | 0.485645 | −0.06793 | 0.043* | |
| N1 | 0.6424 (2) | 0.4329 (2) | 0.02740 (10) | 0.0206 (4) | |
| O1 | 0.0845 (2) | 0.71864 (18) | 0.41231 (7) | 0.0229 (4) | |
| O2 | 0.2353 (2) | 0.41891 (19) | 0.07252 (8) | 0.0276 (4) | |
| H1NA | 0.536 (4) | 0.396 (3) | −0.0024 (15) | 0.031 (6)* | |
| H1NB | 0.736 (5) | 0.344 (4) | 0.0406 (16) | 0.050 (8)* | |
| H2O | 0.127 (6) | 0.348 (4) | 0.0888 (18) | 0.062 (10)* |
Atomic displacement parameters (Å2) top
| U11 | U22 | U33 | U12 | U13 | U23 | |
| C1 | 0.0150 (9) | 0.0248 (9) | 0.0186 (9) | −0.0034 (7) | 0.0013 (7) | −0.0005 (7) |
| C2 | 0.0177 (9) | 0.0271 (9) | 0.0235 (10) | 0.0028 (8) | −0.0013 (7) | 0.0010 (8) |
| C3 | 0.0194 (9) | 0.0307 (9) | 0.0165 (9) | 0.0019 (8) | −0.0029 (8) | 0.0040 (7) |
| C4 | 0.0133 (9) | 0.0285 (9) | 0.0177 (9) | −0.0028 (8) | 0.0000 (7) | −0.0010 (8) |
| C5 | 0.0198 (10) | 0.0253 (9) | 0.0231 (10) | 0.0040 (8) | 0.0010 (8) | 0.0025 (8) |
| C6 | 0.0208 (10) | 0.0292 (9) | 0.0159 (9) | 0.0004 (8) | 0.0000 (8) | 0.0047 (7) |
| C7 | 0.0190 (9) | 0.0269 (9) | 0.0178 (10) | −0.0024 (8) | 0.0003 (7) | −0.0014 (8) |
| C8 | 0.0185 (10) | 0.0253 (9) | 0.0191 (10) | −0.0013 (8) | 0.0015 (8) | −0.0032 (7) |
| C9 | 0.0260 (10) | 0.0358 (10) | 0.0250 (10) | −0.0039 (9) | 0.0067 (9) | 0.0051 (9) |
| N1 | 0.0171 (8) | 0.0279 (8) | 0.0167 (8) | −0.0007 (7) | 0.0017 (6) | 0.0000 (7) |
| O1 | 0.0197 (6) | 0.0316 (7) | 0.0174 (7) | 0.0019 (6) | 0.0025 (6) | −0.0009 (5) |
| O2 | 0.0213 (7) | 0.0431 (9) | 0.0184 (7) | −0.0080 (7) | −0.0004 (5) | −0.0027 (6) |
Geometric parameters (Å, º) top
| C1—C2 | 1.396 (3) | C7—C8 | 1.516 (3) |
| C1—C6 | 1.397 (3) | C7—H7 | 1 |
| C1—C7 | 1.508 (3) | N1—C8 | 1.497 (2) |
| C2—C3 | 1.387 (3) | C8—H8A | 0.99 |
| C2—H2 | 0.95 | C8—H8B | 0.99 |
| C3—C4 | 1.405 (3) | N1—C9 | 1.473 (3) |
| C3—H3 | 0.95 | C9—H9A | 0.98 |
| O1—C4 | 1.335 (2) | C9—H9B | 0.98 |
| C4—C5 | 1.404 (3) | C9—H9C | 0.98 |
| C5—C6 | 1.385 (3) | N1—H1NA | 0.91 (3) |
| C5—H5 | 0.95 | N1—H1NB | 0.95 (3) |
| C6—H6 | 0.95 | O2—H2O | 0.94 (4) |
| O2—C7 | 1.427 (2) | ||
| C2—C1—C6 | 117.69 (16) | C1—C7—H7 | 109.3 |
| C2—C1—C7 | 121.54 (17) | C8—C7—H7 | 109.3 |
| C6—C1—C7 | 120.73 (15) | N1—C8—C7 | 110.55 (16) |
| C3—C2—C1 | 121.18 (18) | N1—C8—H8A | 109.5 |
| C3—C2—H2 | 119.4 | C7—C8—H8A | 109.5 |
| C1—C2—H2 | 119.4 | N1—C8—H8B | 109.5 |
| C2—C3—C4 | 121.21 (16) | C7—C8—H8B | 109.5 |
| C2—C3—H3 | 119.4 | H8A—C8—H8B | 108.1 |
| C4—C3—H3 | 119.4 | N1—C9—H9A | 109.5 |
| O1—C4—C5 | 121.22 (17) | N1—C9—H9B | 109.5 |
| O1—C4—C3 | 121.35 (15) | H9A—C9—H9B | 109.5 |
| C5—C4—C3 | 117.42 (16) | N1—C9—H9C | 109.5 |
| C6—C5—C4 | 120.95 (18) | H9A—C9—H9C | 109.5 |
| C6—C5—H5 | 119.5 | H9B—C9—H9C | 109.5 |
| C4—C5—H5 | 119.5 | C8—N1—C9 | 113.03 (16) |
| C5—C6—C1 | 121.54 (16) | C9—N1—H1NA | 109.8 (15) |
| C5—C6—H6 | 119.2 | C8—N1—H1NA | 109.7 (16) |
| C1—C6—H6 | 119.2 | C9—N1—H1NB | 100.1 (18) |
| O2—C7—C1 | 112.97 (15) | C8—N1—H1NB | 110.7 (16) |
| O2—C7—C8 | 104.80 (15) | H1NA—N1—H1NB | 113 (2) |
| C1—C7—C8 | 111.16 (16) | C7—O2—H2O | 107.8 (19) |
| O2—C7—H7 | 109.3 | ||
| C6—C1—C2—C3 | 0.3 (3) | C7—C1—C6—C5 | 178.52 (18) |
| C7—C1—C2—C3 | −177.39 (17) | O2—C7—C1—C2 | 137.31 (18) |
| C1—C2—C3—C4 | −1.0 (3) | O2—C7—C1—C6 | −40.3 (2) |
| C2—C3—C4—O1 | −178.18 (18) | C2—C1—C7—C8 | −105.2 (2) |
| C2—C3—C4—C5 | 0.6 (3) | C6—C1—C7—C8 | 77.2 (2) |
| O1—C4—C5—C6 | 179.28 (18) | O2—C7—C8—N1 | −60.22 (19) |
| C3—C4—C5—C6 | 0.5 (3) | C1—C7—C8—N1 | 177.43 (15) |
| C4—C5—C6—C1 | −1.3 (3) | C7—C8—N1—C9 | 164.65 (16) |
| C2—C1—C6—C5 | 0.9 (3) |
Hydrogen-bond geometry (Å, º) top
| D—H···A | D—H | H···A | D···A | D—H···A |
| N1—H1NA···O1i | 0.91 (3) | 1.89 (3) | 2.740 (2) | 155 (2) |
| N1—H1NB···O1ii | 0.95 (3) | 1.73 (3) | 2.661 (2) | 164 (3) |
| O2—H2O···O1iii | 0.94 (4) | 1.72 (4) | 2.630 (2) | 162 (3) |
| Symmetry codes: (i) −x+1/2, −y+1, z−1/2; (ii) −x+1, y−1/2, −z+1/2; (iii) −x, y−1/2, −z+1/2. |
Selected comparison of the calculated harmonic frequencies and experimental
wavenumbers (FT–IR) of RS-SYN. top
| FT–IR (cm-1) | Peaks profile* | Calc. freq. (cm-1) | Calc. int. | PEDs (%) | Mode sssign.** |
| 3050–3670 | BVS | 3677 | 37.4 | νO1H(100) | ν(O—H) |
| 3657 | 8.5 | νO2H(100) | ν(O—H) | ||
| 3287 | VS | 3533 | 4.3 | νN1H(99) | ν(N—H) |
| 2983 | M | 3072 | 41.8 | νC8H(91) | ν(C—H) |
| 2959 | M | 3006 | 56.7 | νC7H(93) | ν(C—H) |
| 2877 | M | 2936 | 132.0 | νC9H3(90) | ν(C—H) |
| 1611 | M | 1736 | 67.5 | νC2C3(28)+νC5C6(11) | ν(C═C) |
| 1690 | 5.2 | νC1C6(27)-νC4C5(19) | ν(C═C) | ||
| 1509 | S | 1612 | 88.3 | νC4C5(13)-νC4O1(12) | ν(C—O) |
| 1465 | M | 1509 | 16.9 | δC9N1H(42)-δC7C8N1H(11) | δ(N—H) |
| 1435 | M | 1496 | 22.1 | δC9N1H(24)-δsHC9H(29) | δ(N—H) |
| 1336 | M | 1378 | 93.0 | νC4O1(40) | ν(C—O) |
| 1309 | M | 1345 | 30.0 | νC1C7(15)+δC7O2H(13) | δ(O—H) |
| 1266 | S | 1267 | 10.6 | νC1C7(13)+δN1C8H(10) | δ(C—H) |
| 1260 | 2.4 | νC1C7(16)-δC7O2H(13) | δ(O—H) | ||
| 1205 | M | 1212 | 165.1 | δC4O1H(41)-δC6C5H(10) | δ(O—H) |
| 1097 | S | 1100 | 63.5 | νC7O2(32)-δN1C8H(12) | ν(C—O) |
| 1054 | S | 1070 | 7.9 | νC7C8(21)-νC9N1(11)+δC7O2H(2) | ν(C-N), δ(O—H) |
| 930 | BM | 947 | 16.6 | -νC7C8(19)-νC7O2(25) | ν(C—O) |
| 884 | M | 873 | 40.3 | δC3H(45)+δC2H(31) | δ(C—H) |
| 835 | S | 854 | 30.0 | δC6H(21)+δC5H(62) | δ(C—H)' |
| 780 | M | 767 | 94.7 | -δC9N1H(12)+γC7C8N1H(47) | δ(N—H) |
| 637 | M | 598 | 32.6 | δC4C5C6(22) | δ(C—C) |
| 575 | M | 564 | 32.9 | δC6C7C8(11)+δC8C7O2(12) | δ(C—O) |
| 558 | M | 540 | 3.4 | γO1C4C5C6(14) | γ(C—O) |
| Notes: (*) B = broad, V = very, W = weak, M = medium and S = strong peaks. (**) ν = stretching, δ = bending and γ = rocking vibrations. |
Selected comparison of the calculated harmonic frequencies and experimental
wavenumbers (FT–IR) of R-SYN. top
| FT–IR (cm-1) | Peaks profile* | Calc. freq. (cm-1) | Calc. int. | PEDs (%) | Mode assign.** |
| 3300–3610 | BM | 3712 | 85.2 | νO2H(100) | ν(O—H) |
| 3041 | W | 3204 | 18.1 | νC5H(95) | ν(C—H) |
| 3013 | W | 3200 | 28.1 | νC3H(95) | ν(C—H) |
| 2930–3100 | BM | 3462 | 48.4 | νN1H(94) | ν(N—H) |
| 2938 | VW | 3112 | 19.4 | νC2H(33)+νC6H(64) | ν(C—H) |
| 2871 | VW | 3110 | 61.5 | νC2H(65)-νC6H(34) | ν(C—H) |
| 2590-2880 | BM | 3345 | 68.5 | νN1H(93) | ν(N—H) |
| 2763 | W | 3095 | 10.0 | -νC9H(30)-νC9H(25)-νC9H(44) | ν(C—H) |
| 2723 | W | 2932 | 73.5 | νC7H(90) | ν(C—H) |
| 1605 | BM | 1703 | 38.8 | δsN1H2(87) | δs(N—H) |
| 1558 | M | 1653 | 94.9 | -νC2C3(10)+νC1C6(31) | ν(C═C) |
| 1542 | M | 1644 | 157.4 | -νC2C3(24)+νC4C5(29) | ν(C═C) |
| 1499 | S | 1544 | 18.7 | νC3C4(13) | ν(C═C) |
| 1488 | S | 1534 | 20.0 | δC9H2(38) | δas(C—H) |
| 1527 | 16.5 | δC9H2(43) | δs(C—H) | ||
| 1466 | S | 1503 | 20.9 | δC8H2(39)+δC9H2(18) | δs(C—H) |
| 1499 | 20.6 | -νC2C3(32)+νC5C6(32) | δ(C═C) | ||
| 1426 | M | 1448 | 35.6 | δO2C7H(15) | δ(C—H) |
| 1433 | 166.6 | δHC9N1H1(18)-δHC9N1H2(38) | δs(N—H) | ||
| 1341 | M | 1360 | 69.3 | δC7O2H(16)-δC9N1H(10) | δ(O—H), δ(N—H) |
| 1249 | BVS | 1274 | 185.5 | -νC5C6(12)+νC4O1(54) | ν(C═O) |
| 1272 | 49.7 | -δC7O2H(25)+δO2C7H(21) | δ(O—H) | ||
| 1209 | M | 1214 | 28.4 | -νC6C1(17)+δO2C7H(10) | δ(C—H) |
| 1159 | S | 1187 | 14.6 | δO2C7H(10) | δ(C—H) |
| 1146 | M | 1177 | 118.2 | δC2H(17)+δC3H(17) | δs(C—H) |
| 1077 | M | 1156 | 9.1 | δO2C7H(10)+δC9H3(10) | δ(C—H) |
| 1058 | M | 1115 | 8.4 | δC4C3H(15)+δC6C5H(20) | δ(C—H) |
| 1032 | M | 1073 | 18.7 | νC9N1(69) | ν(C—N) |
| 971 | BM | 1059 | 116.2 | -νC7C8(18)+νC7O2(39) | ν(C—O) |
| 842 | S | 902 | 125.3 | νC8N1(55) | ν(C—N) |
| 802 | M | 849 | 44.7 | γC2H(20) | γ(C—H) |
| 589 | M | 574 | 16.4 | δC3C4C5(22) | δ(C—C) |
| 559 | M | 541 | 32.6 | δC8C7O2(21) | δ(C—O) |
| 469 | M | 430 | 10.1 | δC1C7C8(21)-δC8N1C9(13) | δ(C—N) |
| Notes: (*) B = broad, V = very, W = weak, M = medium and S = strong peaks. (**) ν = stretching, δ = bending and γ = rocking vibrations. |
