Metal complexes bearing vic-dioxime ligands have been extensively used as analytical and biochemical reagents, and are well-known antimicrobial agents. Herein is reported a DFT study on the molecular structures, thermodynamic properties, chemical reactivity and spectral properties of some 3d metal(II) chloride complexes of glyoxime. The functionals B3LYP and CAM-B3LYP have each been used in conjunction with LANL2DZ for the metal(II) ions (Fe 2+, Co 2+, Ni 2+ and Cu 2+) and the Poplestyle basis set 6-31G+(d,p) for the rest of the elements, to perform theoretical calculations. The metal complexation abilities of the glyoxime ligands studied in this work have been evaluated on the basis of metal-ligand binding energies. These ligands were found to have high affinities towards Ni(II) and Fe(II) ions, and all complexation reactions were found to be thermodynamically feasible. Ligand-to-metal electron donations in the complexes studied have been revealed by natural population analysis. The fully optimized geometries of the complexes have adopted square planar structures around the central metal ions. On the basis of orbital composition analysis, the UV-Vis electronic absorption bands of these molecules have been attributed mainly to MLCT, LMCT and d-d electronic transitions involving metal-based orbitals.
The interaction of a central metal with surrounding ligands (atoms, ions or molecules) has been of significant interest in coordination chemistry. In the past decades, the coordination chemistry of transition metal complexes bearing oxime ligands has been a subject of intense studies owing to their applications in many scientific domains like biomedical and electrochemistry. Synthesis of Co(III), Ni(II) and Cu(II) complexes based on two glyoxime derivatives namely: dianiline glyoxime and disulfanilamide glyoxime were envisaged and were found to be effective as stimulators in biosynthetic processes of enzymes in some fungi strains [
Vicinal dioxime derivatives act as amphoteric ligands due to the presence of weak acidic -OH groups and basic -C = N groups. As such, they are capable of forming highly stable complexes with most transition metals in the periodic table. The exceptional stability and electronic properties displayed by these complexes are attributable to their hydrogen bond-stabilized planar structures [
After a detailed literature survey, we have found to the best of our knowledge that very little theoretical studies have been carried out on glyoxime complexes till date [
All theoretical calculations were performed using the Gaussian 09 program package [
The square planar schematic structures of the investigated 3d metal glyoxime complexes, showing atomic numbering are presented in
angles, and dihedral angles) of the ground state geometries of the molecule studied optimized at the DFT/6-31+G(p,d)/(LANL2DZ for metal ions) level, are listed in
Molecules | d(C1-N1) | d(C2-N2) | d(C1-C2) | d(M-N2) | d(M-N1) | d(N1-O1) | d(N2-O2) | d(M-Cl1) | d(M-Cl2) | d(O1-H1) | d(O2-H2) | ||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1a | 1.317 | 1.317 | 1.418 | 1.892 | 1.892 | 1.359 | 1.359 | 2.209 | 2.209 | 0.991 | 0.991 | ||||||
1b | 1.299 | 1.299 | 1.443 | 1.930 | 1.930 | 1.352 | 1.352 | 2.209 | 2.209 | 0.995 | 0.995 | ||||||
1c | 1.292 | 1.292 | 1.456 | 1.929 | 1.929 | 1.346 | 1.346 | 2.198 | 2.198 | 0.999 | 0.999 | ||||||
1d | 1.286 | 1.286 | 1.468 | 2.092 | 2.092 | 1.346 | 1.346 | 2.263 | 2.263 | 0.997 | 0.997 | ||||||
2a | 1.324 | 1.324 | 1.441 | 1.877 | 1.877 | 1.366 | 1.366 | 2.220 | 2.220 | 0.992 | 0.992 | ||||||
2b | 1.303 | 1.302 | 1.469 | 1.915 | 1.924 | 1.360 | 1.360 | 2.217 | 2.217 | 0.996 | 0.996 | ||||||
2c | 1.302 | 1.302 | 1.480 | 1.922 | 1.922 | 1.355 | 1.355 | 2.204 | 2.204 | 0.998 | 0.998 | ||||||
2d | 1.291 | 1.290 | 1.494 | 2.063 | 2.075 | 1.356 | 1.356 | 2.266 | 2.270 | 0.996 | 0.996 | ||||||
3a | 1.328 | 1.328 | 1.450 | 1.876 | 1.770 | 1.365 | 1.365 | 2.221 | 2.221 | 0.993 | 0.993 | ||||||
3b | 1.308 | 1.308 | 1.479 | 1.916 | 1.916 | 1.359 | 1.359 | 2.218 | 2.218 | 0.996 | 0.996 | ||||||
3c | 1.302 | 1.302 | 1.492 | 1.915 | 1.915 | 1.354 | 1.354 | 2.205 | 2.205 | 0.999 | 0.999 | ||||||
3d | 1.296 | 1.296 | 1.504 | 2.045 | 2.045 | 1.362 | 1.362 | 2.298 | 2.298 | 0.987 | 0.987 | ||||||
4a | 1.366 | 1.366 | 1.426 | 1.810 | 1.810 | 1.357 | 1.357 | 2.228 | 2.228 | 0.994 | 0.994 | ||||||
4b | 1.319 | 1.319 | 1.461 | 1.901 | 1.901 | 1.357 | 1.357 | 2.213 | 2.213 | 0.994 | 0.994 | ||||||
4c | 1.308 | 1.308 | 1.473 | 1.916 | 1.916 | 1.351 | 1.351 | 2.201 | 2.201 | 0.998 | 0.998 | ||||||
4d | 1.301 | 1.301 | 1.488 | 2.072 | 2.072 | 1.350 | 1.350 | 2.268 | 2.268 | 0.997 | 0.997 | ||||||
d(H1-Cl1) | d(H2-Cl2) | ɵ(Cl1-M-Cl2) | ɵ(N1-M-N2) | ɵ(O1-H-Cl1) | ɵ(O2-H2-Cl2) | ɵ(Cl1-M-N2) | Φ(Cl1-M-N1-C1) | Φ(M-N1-C1-C2) | |||||||||
1a | 2.170 | 2.170 | 97.537 | 81.403 | 138.997 | 138.997 | 171.93 | −179.998 | 0.0026 | ||||||||
1b | 2.143 | 2.143 | 98.004 | 80.785 | 141.100 | 141.100 | 171.390 | −179.994 | 0.0008 | ||||||||
1c | 2.112 | 2.112 | 97.271 | 80.943 | 142.176 | 142.176 | 171.836 | −179.999 | 0.000 | ||||||||
1d | 2.174 | 2.174 | 105.963 | 75.999 | 144.786 | 144.786 | 165.018 | −179.996 | −0.001 | ||||||||
2a | 2.139 | 2.139 | 97.189 | 80.763 | 140.723 | 140.723 | 171.787 | 180.000 | 0.000 | ||||||||
2b | 2.108 | 2.122 | 97.582 | 80.189 | 143.262 | 142.306 | 171.411 | −179.987 | −0.001 | ||||||||
2c | 2.085 | 2.098 | 96.768 | 80.334 | 144.045 | 143.099 | 171.895 | −179.983 | −0.034 | ||||||||
2d | 2.143 | 2.153 | 104.809 | 75.584 | 146.729 | 145.838 | 165.500 | −179.980 | −0.006 | ||||||||
3a | 2.109 | 2.109 | 96.254 | 81.053 | 142.191 | 142.190 | 172.398 | −179.046 | −1.980 | ||||||||
3b | 2.090 | 2.090 | 96.717 | 80.282 | 144.037 | 144.036 | 171.774 | −179.057 | −3.410 | ||||||||
3c | 2.063 | 2.063 | 95.941 | 80.411 | 144.867 | 144.867 | 172.230 | −178.649 | −4.120 | ||||||||
3d | 2.209 | 2.209 | 100.022 | 76.836 | 145.735 | 145.735 | 168.406 | −175.926 | −9.933 | ||||||||
4a | 2.110 | 2.110 | 95.050 | 84.033 | 139.431 | 139.436 | 174.494 | −179.994 | 0.001 | ||||||||
4b | 2.130 | 2.130 | 96.668 | 81.852 | 141.140 | 141.159 | 172.588 | −179.985 | 0.002 | ||||||||
4c | 2.101 | 2.102 | 96.654 | 81.487 | 142.431 | 142.431 | 172.411 | −179.992 | 0.006 | ||||||||
4d | 2.152 | 2.151 | 105.004 | 76.575 | 145.558 | 145.580 | 165.777 | −179.993 | 0.011 | ||||||||
These values ought to be compared with those obtained experimentally, but X-ray crystallographic data is not available in the literature for these complexes. It is clear from the values in
It is evident from
In order to investigate thermodynamic properties of complexation reactions, statistical thermodynamic calculations were carried out at 1 atm and 298.15 K. To investigate the stability of the complexes studied, the thermodynamic parameters: binding energy (∆Eint), Gibbs free energy (∆G˚) and enthalpy (∆H˚) of formation were calculated.
The complexation ability of the ligands with different metal cations is characterized by their binding energy as defined in Equation (1).
where EComplex, ELigand, EMetal(II) and ECl are respectively the thermal energy of complex, free glyoxime ligand, free metal ions and free chloride ligands.
A large variation in the complexation energies is clear from
Molecules | ∆G2980(react) | ∆H2980(react) | ∆E(react) |
---|---|---|---|
1a | −644 | −670 | −669 |
1b | −635 | −661 | −660 |
1c | −674 | −700 | −698 |
1d | −626 | −651 | −649 |
2a | −644 | −671 | −669 |
2b | −635 | −662 | −660 |
2c | −675 | −702 | −700 |
2d | −626 | −653 | −651 |
3a | −636 | −664 | −662 |
3b | −628 | −655 | −654 |
3c | −667 | −695 | −693 |
3d | −634 | −660 | −658 |
4a | −660 | −686 | −684 |
4b | −643 | −669 | −668 |
4c | −680 | −706 | −705 |
4d | −631 | −656 | −654 |
values have been obtained for the formation of the Cu(II) complexes. Hence, the ligands exhibit their greatest affinity toward the Ni(II) ion and the least toward the Cu(II) ion. For instance, the complexation energy for the formation of 1d is higher than that of formation of 1c by 49 kcal∙mol−1. Generally, more negative complexation energies are more thermodynamically favored. Based on this fact, it can be concluded that the formation of the Ni(II) complexes is most favorable of all the complexes investigated. It is worthy of note that the formation processes for the complexes bearing ligand 4 are most favored.
Besides binding energies, the standard complexation Gibbs free energy (∆G˚) and enthalpy change (∆H˚) were also calculated using Equations (2) and (3) and the results are presented in
It is clear from
The NPA charges on the metal(II) ions in the complexes investigated are listed in
Molecules | M | Cl1 | Cl2 | N1 | N2 | O1 | O2 | C1 | C2 | H1 | H2 |
---|---|---|---|---|---|---|---|---|---|---|---|
1 | - | - | - | −0.12946 | −0.05480 | −0.63148 | −0.56382 | −0.04738 | −0.11855 | 0.53571 | 0.49630 |
1a | 0.37074 | −0.34660 | −0.34660 | −0.09933 | −0.09933 | −0.53319 | −0.53319 | 0.00033 | 0.00033 | 0.52905 | 0.52905 |
1b | 0.46007 | −0.39576 | −0.39576 | −0.10306 | −0.10306 | −0.53038 | −0.53038 | 0.00753 | 0.00753 | 0.52923 | 0.52923 |
1c | 0.40726 | −0.38906 | −0.38906 | −0.08747 | −0.08747 | −0.52606 | −0.52606 | 0.00923 | 0.00924 | 0.52805 | 0.52805 |
1d | 0.72555 | −0.48898 | −0.48898 | −0.14004 | −0.14004 | −0.53103 | −0.53103 | 0.00954 | 0.00954 | 0.53189 | 0.53189 |
2 | - | - | - | −0.13289 | −0.13289 | −0.61469 | 0.51882 | 0.18622 | 0.18622 | 0.51882 | 0.51882 |
2a | 0.36531 | −0.36627 | −0.36627 | −0.09941 | −0.09941 | −0.54727 | −0.54727 | 0.21806 | 0.21806 | 0.52897 | 0.52897 |
2b | 0.45630 | −0.40887 | −0.40947 | −0.10859 | −0.10897 | −0.54964 | −0.54711 | 0.22685 | 0.22685 | 0.52814 | 0.52814 |
2c | 0.40617 | −0.40062 | −0.40004 | −0.09617 | −0.09557 | −0.54387 | −0.54638 | 0.22851 | 0.22804 | 0.52797 | 0.52709 |
2d | 0.72771 | −0.49620 | −0.49765 | −0.15248 | −0.15187 | −0.55224 | −0.55080 | 0.22756 | 0.22794 | 0.53073 | 0.53134 |
3 | - | - | - | −0.14296 | −0.04334 | −0.62093 | −0.54271 | 0.13935 | 0.07813 | 0.53767 | 0.50029 |
3a | 0.37099 | −0.36471 | −0.36468 | −0.09323 | −0.09297 | −0.54174 | −0.54176 | 0.22012 | 0.21845 | 0.52582 | 0.52582 |
3b | 0.45920 | −0.40725 | −0.40728 | −0.10386 | −0.10359 | −0.54208 | −0.54210 | 0.22824 | 0.22662 | 0.52554 | 0.52554 |
3c | 0.40843 | −0.39868 | −0.39867 | −0.09091 | −0.09063 | −0.53927 | −0.53930 | 0.22940 | 0.22780 | 0.52433 | 0.52433 |
3d | 0.73010 | −0.50412 | −0.50412 | −0.15355 | −0.15355 | −0.54451 | −0.54451 | 0.23284 | 0.23284 | 0.53357 | 0.53357 |
4 | - | - | - | −0.13592 | −0.14087 | −0.60406 | −0.58988 | 0.17596 | 0.20040 | 0.52151 | 0.51776 |
4a | 0.31307 | −0.35301 | −0.35295 | −0.05147 | −0.05145 | −0.52723 | −0.52723 | 0.14946 | 0.14946 | 0.52840 | 0.52838 |
4b | 0.46580 | −0.39199 | −0.39199 | −0.09457 | −0.09457 | −0.53871 | −0.53869 | 0.17451 | 0.17452 | 0.52943 | 0.52943 |
4c | 0.41231 | −0.39118 | −0.39112 | −0.07825 | −0.07823 | −0.53415 | −0.53415 | 0.17752 | 0.17753 | 0.52857 | 0.52854 |
4d | 0.72930 | −0.49416 | −0.49411 | −0.13332 | −0.13358 | −0.53847 | −0.53856 | 0.17737 | 0.17723 | 0.53207 | 0.53203 |
by the complexation energies (
The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are very important parameters for quantum chemistry. The frontier orbital gap helps to characterize the chemical reactivity and kinetic stability of molecules. A molecule with a small frontier orbital gap is more polarizable and is generally associated with a high chemical reactivity, low kinetic stability and is also termed soft molecule. The eigenvalues of the HOMO and LUMO as well as their energy gap reflect the chemical reactivity of a molecule. A large HOMO-LUMO energy gap has been associated with high stability of molecules [
The values of some global reactivity descriptors investigated in this paper are presented in
Molecules | EHOMO | ELUMO | ∆EH-L | µ | ɳ | w | S |
---|---|---|---|---|---|---|---|
1a | −7.22 | −4.53 | 2.68 | −5.87 | 1.34 | 12.85 | 0.37 |
1b | −7.76 | −3.85 | 3.91 | −5.80 | 1.96 | 8.60 | 0.26 |
1c | −7.44 | −3.85 | 3.59 | −5.65 | 1.79 | 8.89 | 0.28 |
1d | −7.71 | −3.83 | 3.88 | −5.78 | 1.94 | 8.59 | 0.26 |
2a | −6.82 | −4.15 | 2.66 | −5.48 | 1.33 | 1.30 | 0.38 |
2b | −7.45 | −3.31 | 4.14 | −5.38 | 2.07 | 6.99 | 0.24 |
2c | −7.14 | −3.30 | 3.85 | −5.22 | 1.92 | 7.09 | 0.26 |
2d | −7.42 | −3.28 | 4.14 | −5.35 | 2.07 | 6.92 | 0.24 |
3a | −6.65 | −4.12 | 2.53 | −5.39 | 1.26 | 11.47 | 0.40 |
3b | −7.26 | −3.40 | 3.86 | −5.33 | 1.93 | 7.36 | 0.26 |
3c | −7.02 | −3.40 | 3.63 | −5.21 | 1.81 | 7.48 | 0.28 |
3d | −7.25 | −3.18 | 4.07 | −5.22 | 2.04 | 6.69 | 0.25 |
4a | −7.13 | −4.44 | 2.69 | −5.78 | 1.34 | 12.42 | 0.37 |
4b | −6.99 | −4.34 | 2.66 | −5.67 | 1.32 | 12.09 | 0.38 |
4c | −6.96 | −4.34 | 2.62 | −5.65 | 1.31 | 12.18 | 0.38 |
4d | −7.18 | −4.38 | 2.80 | −5.78 | 1.40 | 11.91 | 0.36 |
To the best of our knowledge, no IR spectral data is available in the literature for the complexes investigated in this research endeavor. The DFT/B3LYP method in conjunction with a doubly split valence basis set along with diffuse and polarization functions, 6-31+G(d,p) and LANL2DZ for the central metal(II) ions was used to calculate harmonic vibrational frequencies of the glyoximes complexes studied. IR frequencies of two complexes (1a’ and 1b’) were also calculated using different basis set (B3LYP/6-31+ G(d,p)/SDD for metal ion) with same method in order to study the effect of basis set in the frequency calculation. The Gauss View 5.0.8 molecular visualization program was used to perform the IR vibrational band assignments for the molecules. Although experimentally determined IR vibrational frequencies were not available for these molecules, the calculated values were still scaled down because the DFT/B3LYP method tends to overestimate normal mode frequencies due to a combination of electron correlation effects and basis set deficiencies [
IR vibrations of the OH group are generally found to be most sensitive to the environment. As such, they show pronounced shifts in the spectra of the hydrogen-bonded species. The optimum absorption region of non-hydrogen bonded or a free hydroxyl group is 3550 - 3700 cm−1 [
As a general observation in
The absorption spectral simulation of 3d metal(II) glyoximes complexes have been performed using Time-Dependent DFT calculations at the Cam-B3LYP/6-31G+(d,p)/ (LanL2DZ for metal(II) ions) levels of theory in gas phase. The calculated absorption energy, corresponding oscillator strength and orbital coefficients are summarized in
Molecules | ῡ(O-H) | ῡ(C = N) | ῡ(N-O) | ῡ(C-C) | ῡ(C-H) |
---|---|---|---|---|---|
1 | 3331 - 3668 | 1558 - 1638 | 863 | 1307 | 3045 - 3055 |
1a | 3246 - 3252 | 1500 - 1566 | 1091 - 1130 | 1439 | 3110 - 3119 |
1a’ | 3268 - 3274 | 1500 - 1568 | 1090 - 1124 | 1441 | 3108 - 3117 |
1b | 3166 - 3179 | 1569 | 1115 - 1136 | 1457 | 3097 - 3107 |
1b’ | 3183 - 3196 | 1565 - 1617 | 1109 - 1132 | 1452 | 3097 - 3108 |
1c | 3107 - 3126 | 1602 - 1640 | 1138 - 1148 | 1462 | 3093 - 3103 |
1d | 3151 - 3169 | 1608 - 1661 | 1135 - 1143 | 1465 | 3072 - 3081 |
2 | 3676 - 3678 | 1608 - 1651 | 879 - 928 | 1355 | 2933 - 3027 |
2a | 3219 - 3225 | 1517 - 1572 | 1071 - 1186 | 1517 | 2938 - 3055 |
2b | 3151 - 3167 | 1584 - 1637 | 1093 - 1192 | 1449 | 2934 - 3059 |
2c | 3103 - 3124 | 1617 - 1656 | 1113 - 1199 | 1454 | 2933 - 3059 |
2d | 3147 - 3165 | 1619 - 1672 | 1109 - 1183 | 1456 | 2934 - 3057 |
3 | 3231 - 3665 | 1485 - 1557 | 921 - 1059 | 1234 | 3069 - 3101 |
3a | 3202 - 3209 | 1515 - 1552 | 1082 - 1108 | 1427 | 3066 - 3100 |
3b | 3134 - 3150 | 1574 - 1608 | 1087 - 1106 | 1430 | 3067 - 3101 |
3c | 3082 - 3101 | 1625 - 1601 | 1073 - 1116 | 1434 | 3101 - 3068 |
3d | 3298 - 3303 | 1595 - 1637 | 1071 - 1098 | 1426 | 3074 - 3103 |
4 | 3671 - 3673 | 1617 - 1623 | 932 | 1335 | 3058 - 3133 |
4a | 3176 - 3182 | 1564 | 1047 - 1141 | 1554 | 3080 - 3122 |
4b | 3175 - 3188 | 1555 - 1606 | 1038 - 1077 | 1482 | 3079 - 3123 |
4c | 3106 - 3127 | 1585 - 1623 | 1042 - 1110 | 1507 | 3079 - 3121 |
4d | 3129 - 3151 | 1585 - 1634 | 1033 - 1114 | 1437 | 3078 - 3120 |
1a’: Calculated frequencies of Fe(II) complex with ligand 1 at B3LYP/6-31+G(d,p)/(SDD for metal ion). 1b’: Calculated frequencies of Co(II) complex with ligand 1 at B3LYP/6-31+G(d,p)/(SDD for metal ion).
For the first series of complexes, the most intense band was observed at: 295.02, 326.80, 216.88 and 264.83 nm for the 1a, 1b, 1c and 1d complexes respectively. As evidenced in
Molecules | Orbital transition | Energy (ev) | Wavelength (nm) | Oscillator strength | Character |
---|---|---|---|---|---|
1a | HOMO − 2 → LUMO + 1 (0.67) | 4.2026 | 295.02 | 0.1634 | ILCT/LMCT/LLCT |
1b | HOMO − 2 → LUMO (0.72) | 3.7938 | 326.80 | 0.0576 | MLCT/LLCT |
1c | HOMO − 7 → LUMO + 1 (0.62) | 5.7167 | 216.88 | 0.4923 | LMCT/LLCT/ILCT/d-d/MLCT |
1d | HOMO − 2 → LUMO (0.56) | 4.6816 | 264.83 | 0.2186 | ILCT |
2a | HOMO − 2 → LUMO (0.54) | 3.4760 | 356.69 | 0.1588 | LMCT/LLCT/ILCT |
2b | HOMO − 2 → LUMO (0.59) | 3.9155 | 316.65 | 0.0586 | LLCT/MLCT |
2c | HOMO − 8 → LUMO + 1 (0.62) | 5.7857 | 214.29 | 0.4516 | LMCT/LLCT/ILCT/d-d/MLCT |
2d | HOMO → LUMO + 1 (0.70) | 4.5480 | 272.61 | 0.1389 | LLCT/ILCT |
3a | HOMO − 2 → LUMO (0.45) | 3.3972 | 364.96 | 0.3154 | LMCT/ILCT |
3b | HOMO − 1 → LUMO (0.53) | 3.7523 | 330.42 | 0.1235 | d-d/ILCT/LMCT |
3c | HOMO − 1 → LUMO (0.64) | 4.0710 | 304.56 | 0.2843 | ILCT/LLCT |
3d | HOMO − 10 → LUMO (0.96) | 3.6437 | 340.27 | 0.1971 | LMCT/LLCT/ILCT/d-d/MLCT |
4a | HOMO − 4 → LUMO + 1 (0.48) | 3.1790 | 390.02 | 0.2849 | LMCT/LLCT/ILCT/d-d/MLCT |
4b | HOMO → LUMO (0.72) | 2.6979 | 459.55 | 0.0792 | ILCT/LMCT |
4c | HOMO − 3 → LUMO (0.66) | 3.5501 | 349.24 | 0.1166 | LLCT/MLCT |
4d | HOMO − 6 → LUMO + 1 (0.97) | 3.7972 | 326.52 | 0.1290 | LMCT/ILCT/LLCT |
bands of this series of complexes are in the decreasing order: 1c > 1a > 1d > 1b.
The transition energy is inversely proportional to the absorption wavelength in each case, for instance, complex 1c has a high absorption energy (5.7167 ev) corresponding to the HOMO − 7 → LUMO + 1 electronic transition, which is observed at the wavelength 216.88 nm. The molecular orbital compositions in
For the second series of complexes containing dimethylglyoxime as one of the ligands, the maximum absorption bands appeared at: 356.69, 316.65, 214.29 and 272.61 nm for the 2a, 2b, 2c and 2d complexes respectively. It is clear from
Molecules | Orbital | Index | M | 2Cl− | L | Main bond type |
---|---|---|---|---|---|---|
1a | HOMO − 2 | 46 | 2.46 | 23.82 | 73.72 | π(L) + p(Cl) |
LUMO + 1 | 50 | 16.51 | 2.8 | 80.69 | π*(L) + d(Fe) | |
1b | HOMO − 2 | 47A | 27.55 | 67.24 | 5.20 | p(Cl) + d(Co) |
LUMO | 50A | 9.41 | 1.67 | 88.92 | π*(L) | |
1c | HOMO − 7 | 42 | 17.71 | 64.44 | 17.85 | p(Cl) + π(L) + d(Ni) |
LUMO + 1 | 51 | 61.81 | 23.18 | 15.01 | d(Ni) + p(Cl) + π*(L) | |
1d | HOMO − 2 | 45B | 1.00 | 5.47 | 93.53 | π(L) |
LUMO | 51B | 5.46 | 1.08 | 93.45 | π*(L) | |
2a | HOMO − 2 | 54 | 2.63 | 22.25 | 75.11 | π(L) + p(Cl) |
LUMO | 57 | 79.19 | 10.15 | 10.66 | d(Fe) + π*(L) + p(Cl) | |
2b | HOMO − 2 | 55A | 31.11 | 62.64 | 6.26 | p(Cl) + d(Co) |
LUMO | 58A | 9.11 | 1.61 | 89.28 | π*(L) | |
2c | HOMO − 8 | 49 | 15.60 | 65.56 | 18.83 | p(Cl) + π(L) + d(Ni) |
LUMO + 1 | 59 | 62.15 | 22.34 | 15.51 | d(Ni) + p(Cl) + π(L) | |
2d | HOMO | 57B | 6.43 | 80.68 | 12.89 | p(Cl) + π(L) |
LUMO + 1 | 59B | 6.19 | 1.26 | 92.55 | π*(L) | |
3a | HOMO − 2 | 86 | 2.58 | 8.48 | 88.94 | π(L) |
LUMO | 89 | 76.66 | 9.91 | 13.42 | d(Fe) + π*(L) | |
3b | HOMO − 1 | 88A | 41.66 | 24.01 | 34.34 | d(Co) + π(L)+ p(Cl) |
LUMO | 90A | 62.15 | 6.02 | 31.83 | d(Co) + π*(L) | |
3c | HOMO − 1 | 88 | 9.24 | 20.88 | 69.88 | π(L) + p(Cl) |
LUMO | 90 | 7.95 | 1.49 | 90.56 | π*(L) | |
3d | HOMO − 10 | 79B | 17.91 | 61.05 | 21.04 | p(Cl) + π(L) + d(Cu) |
LUMO | 90B | 54.44 | 28.18 | 17.38 | d(Cu) + p(Cl) + π*(L) | |
4a | HOMO − 4 | 57 | 14.33 | 72.88 | 12.78 | p(Cl) + d(Fe) + π(L) |
LUMO + 1 | 63 | 68.04 | 8.30 | 23.66 | d(Fe) + π*(L) | |
4b | HOMO | 61B | 2.61 | 4.50 | 92.89 | π(L) |
LUMO | 62B | 13.47 | 2.19 | 84.34 | π*(L) + d(Co) | |
4c | HOMO − 3 | 59 | 24.26 | 69.45 | 6.10 | p(Cl) + d(Ni) |
LUMO | 63 | 7.00 | 1.22 | 84.38 | π*(L) | |
4d | HOMO − 6 | 56B | 17.84 | 61.48 | 20.36 | p(Cl) |
LUMO + 1 | 64B | 57.12 | 28.23 | 14.41 | d(Cu) + p(Cl) + π*(L) |
character of the most intense band in 2c is principally ligand-to-metal charge transfer (LMCT).
In the case of the third series, the maximum absorption bands are: 364.96, 330.42, 304.56 and 340.27 nm corresponding to the 3a, 3b; 3c and 3d complexes respectively. Hence, the most intense band with high oscillator strength (0.3154) is exhibited by 3a. The intensities of the dominant transitions in this series can be classified in the increasing order: 3a > 3c > 3d > 3b (
For the last series of complexes studied, the maximum absorption bands are respectively 390.02, 459.55, 349.24 and 326.52 nm for the 4a; 4b; 4c and 4d complexes. Clear from
DFT and TD-DFT calculations were used to investigate the molecular properties of some 3d metal (II) chloride glyoxime complexes. The optimized geometries of the complexes studied revealed a nearly square planar geometry around the central metal ion in each complex. Our results showed the existence of hydrogen bonds between the two OH groups of glyoxime and the two chloride ligands in all complexes investigated, which significantly contribute toward the stabilization of the complexes. As a general observation for all the metal ions studied, the ligands showed the greatest affinity toward the nickel(II) ion and the least affinity toward copper(II) ion. For the complexes studied, all complexation reactions were found to be thermodynamically feasible and exothermic. Natural population analysis showed the possibility of ligand-to-metal charge transfer. Electronic absorption bands obtained in the UV/Visible region have been attributed mainly to MLCT, LMCT and d-d electronic transitions involving metal-based orbitals.
The authors are thankful to the IIT Kanpur, India for the resources made available through a CV Raman International Fellowship award (Grant No. 101F102), offered by the Ministry of External Affairs of India and FICCI (Federation of Indian Chambers of Commerce and Industry).
Nogheu, L.N., Ghogomu, J.N., Mama, D.B., Nkungli, N.K., Younang, E. and Gadre, S.R. (2016) Structural, Spectral (IR and UV/Visible) and Thermodynamic Properties of Some 3d Transition Metal(II) Chloride Complexes of Glyoxime and Its Derivatives: A DFT and TD-DFT Study. Computational Chemistry, 4, 119-136. http://dx.doi.org/10.4236/cc.2016.44011