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Innovative Medicines & Omics Synthesis and docking of diorganotin (IV) chelates

chemical shift values are summarized in Table 4. Comparing substituents are δ −116.2 and −105.9, respectively, whereas
the position of the C carbon signal in organotin (IV) for ethyl group is observed at δ −143.6.
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chelates with its position in the Schiff bases, an up-field The MW analysis conducted in chloroform solution
4
shift is observed. Further, a downfield shift is observed for at 45°C demonstrated that these compounds exist as
the C and C carbon signals. The signal for the ring methyl monomers. Spectroscopic analysis revealed that the Schiff
4
3
carbon resonates in the range of δ 15.20 – 17.51 ppm. In bases act as bifunctional tridentate ligands. Analysis of
Chelate-2 and Chelate-4, the terminal carbon signals are the Sn NMR spectra indicated that the Sn atom exhibits
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observed at δ 9.17 – 11.87 ppm for the –CH group and δ pentacoordinate geometry. 35
2
32.84 – 33.32 ppm for the –CH group. The carbon atom
3
of the methyl group bonded to the Sn atom shows a signal 3.2. DFT calculations
in the range of δ 7.87 – 8.87 ppm. The butyl carbon signals
attached to the central Sn atom are observed at δ 13.52 – Using DFT, we analyzed the comparative reactivity patterns
29.30 ppm. The terminal C H /C H Cl, ring phenyl, and of various Sn complexes. The analysis incorporated
4
6
5
6
thiophenol ring carbon atoms are observed at δ 115.09 – multiple reactivity descriptors, examining both global
149.09 ppm. Therefore, C NMR spectral evidence is also parameters (electrophilic and nucleophilic character) and
13
in agreement with IR and H NMR spectral studies. their localized counterparts.
1
The study included calculations of fundamental
3.1.4. Sn NMR spectra electronic properties, such as the highest occupied electron
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The 119 Sn NMR spectra of these chelates were recorded orbital (HOMO) and lowest unoccupied molecular orbital
in chloroform, with tetramethyltin used as an external (LUMO) energy levels. These molecular orbital energies
reference. Sn NMR spectroscopy is one of the specialized were used to derive key chemical descriptors, including
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techniques that provide necessary information on the the molecule’s ability to donate (ionization potential) and
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structures of organotin compounds. Values of chemical accept (electron affinity) electrons, chemical hardness and
shift observed in the case of phenyl and chlorophenyl electronegativity, electrophilic behavior, and electronic
chemical potential. These correlations provide insights
Table 4. The C nuclear magnetic resonance spectral data of into the molecular characteristics of the complexes.
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organotin (IV) complexes (in δ ppm)
3.2.1. Geometrical parameters
Parameter Chelate 1 Chelate 2 Chelate 3 Chelate 4
C (C=O) 161.68 160.5 162.2 162.09 The DFT-optimized geometry of the Sn chelates is depicted
3 in Figure 2, and the corresponding bond lengths and bond
C (C=N) 104.56 103.85 104.4 104.29 angles for the Sn complexes are listed in Table 5. In the Sn
2+
4
C (C=N–N) 138.22 138.8 138.58 138.1
5 complexes, Mulliken charge analysis was performed for Sn
C (C=NR’) 192.68 197.7 191.9 190.65 and the coordinating atoms (O, S, nitrogen [N]), as well as
6
C (CH on pyrazolone) 17.34 15.2 16.1 16.31 the two methyl groups. This analysis indicates that electron
7 3
–CH (R’ in chelate 2) – 11.87 – – transfer from the ligands to Sn is consistent across all
2
–CH (R’ in chelate 1 and 2) 27.82 33.32 – – chelates, regardless of the substituent. Upon complexation,
3
–C H (R’ in chelate 3) – – 137.72 – Sn experiences a loss of approximately 0.7e, resulting in
6
5
a charge of +1.325 (down from +2). The coordinating
–C H Cl (R’ in chelate 4) – – – 128.78
6 4 atoms, O and N, possess similar Mulliken charges (−0.55
Ring phenyl (N1-Phenyl, 148.56 148.34 149.09 148.77 and −0.60, respectively), while S carries a slightly smaller
C-ipso) charge (−0.2).
Ring phenyl (C-ortho) 128.8 128.83 128.89 128.94
In the optimized structures, the bond distances
Ring phenyl (C-meta) 125.43 126.89 126.12 126.39 between Sn and the heteroatoms O and N are 2.1 Å and 2.2
Ring phenyl (C-para) 121 121.04 121.03 121.09 Å, respectively, whereas the Sn–S bond distance is longer,
Thiophenol ring (C-ipso, 115.16 115.29 115.44 115.24 at 2.6 Å. The bond lengths for the two methyl groups
C–S–Sn) covalently bonded to Sn (Sn–C8 and Sn–C8’) are shorter,
Thiophenol ring (C-para) 118.67 119.08 119.63 118.62 measuring 2.1 Å. Notable differences in coordinating bond
Thiophenol ring 118.14 117.68 118.9 116.68 angles are observed as a result of steric effects, particularly
(C-ortho) when substituting methyl groups with chlorophenyl rings.
Thiophenol ring (C-meta) 121 121.04 120.73 120.88 The bond angles between the two methyl groups attached
Sn–R (aliphatic) 8.87 7.87 8.78 8.41 to the Sn ion (C8’–Sn–C) fall within the range of 126° –
Abbreviation: R: Functional group. 127°, while the ∠O–Sn–N angles range from 80° to 81°, and
Volume 2 Issue 3 (2025) 72 doi: 10.36922/IMO025140019