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

affinity refers to the energy released when an electron is orbital distributions revealed distinct electronic patterns:
added to the molecule, and higher values imply a greater the highest occupied state showed significant electron
tendency to accept electrons. density around the S-containing portion of the molecule,
According to calculations performed using the B3LYP/ whereas the lowest unoccupied state exhibited electron
LanL2DZ method, the predicted HOMO and LUMO values density spread across both the imidazole moiety and S
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for the Sn chelates are −0.20 eV and −0.08 eV, respectively. region. We employed Koopman’s theorem, which applies
From these values, the HOMO-LUMO energy gap (∆E) is to closed-shell systems, to compute global reactivity
calculated to be 0.12 eV, indicating the molecule’s electronic parameters.
properties. As observed in Figure 3, analysis of the frontier Our findings from these calculations were quantitatively
documented in Table 5. The ionization potential of the
Table 5. Selected molecular parameters and dipole moment complexes is 0.20 eV, and the electron affinity (A) is in the
(debye) of organotin (IV) complexes range of 0.076 – 0.089 eV. The hardness of the complexes is
calculated to be approximately 0.06 eV across all chelates.
Parameter Chelate‑1 Chelate‑2 Chelate‑3 Chelate‑4 However, the softness values for the methyl (Chelate-1)
Dipole moment 3.010 2.856 3.440 2.129 and ethyl (Chelate-2) substituents are around 7.8, while
Mulliken charge (e) for phenyl (Chelate-3) and chlorophenyl (Chelate-4)
Sn 1.326 1.325 1.325 1.325 substituents, they are slightly higher, at 8.4 and 8.6,
O −0.557 −0.555 −0.546 −0.546 respectively, indicating increased reactivity in the phenyl-
N −0.568 −0.590 −0.584 −0.581 substituted compounds. The electrophilicity index of the
S −0.192 −0.198 −0.196 −0.193 complexes is calculated to be 0.001 eV, which is relevant for
Bond angle (°) describing their biological activity. The chemical potential
O–Sn–N 81.390 81.034 80.969 80.833 of the complexes is −0.14 eV, a negative value, suggesting
that these complexes are chemically stable.
N–Sn–S 78.248 77.973 77.772 77.656
S–Sn–C25 120.754 95.626 100.919 101.067 3.3. Docking analysis
S–Sn–C26 101.030 101.445 96.515 96.654 We performed molecular docking simulations on the
C25–Sn–C26 126.164 125.688 126.612 126.499 above DFT-optimized structures. The docking analysis
Bond distance (Å) utilized cephalosporin and sulfamethoxazole as reference
O–Sn 2.134 2.135 2.148 2.148 ligands for transpeptidase and dihydropteroate synthase,
N–Sn 2.185 2.177 2.177 2.180 respectively, to benchmark the binding affinities of the
S–Sn 2.611 2.617 2.612 2.611 ligands (L-1 to L-4) against selected bacterial target
proteins (5TW8, 6NTW, 1AD4, and 5V7A), as shown in
Sn–C26 2.118 2.118 2.118 2.117
Table 7. Molecular docking was conducted using only the
C25–Sn 2.128 2.128 2.127 2.127 ligand moieties of the organotin (IV) complexes, with the

Table 6. Global reactivity descriptors and energies of organotin (IV) complexes on the B3LYP/LanL2DZ basis set
Molecular properties Expression Chelate‑1 Chelate‑2 Chelate‑3 Chelate‑4
E , ev Energy of H −0.204 −0.203 −0.202 −0.207
HOMO OMO
E , ev Energy of L −0.076 −0.077 −0.083 −0.090
LUMO UMO
E , ev E −E 0.128 0.127 0.119 0.117
Gap HOMO LUMO
Ionization potential, ev −E HOMO 0.204 0.203 0.202 0.207
Electron affinity, ev −E LUMO 0.076 0.077 0.083 0.090
Chemical hardness (η), ev 1/2 (E LUMO −E HOMO ) 0.064 0.063 0.059 0.058
Softness, S 1/2η 7.829 7.883 8.408 8.559
Chemical potential (µ), ev 1/2 (E LUMO +E HOMO ) −0.140 −0.140 −0.143 −0.148
Electronegativity (χ), ev −1/2 (E LUMO +E HOMO ) 0.140 0.140 0.143 0.148
Electrophilicity index (ω), ev µ /2η 0.001 0.001 0.001 0.001
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Optimized energy, au E −1,027.7 −1,066.9 −1,219.4 −1,233.7
Abbreviations: HOMO: Highest occupied electron orbital; LUMO: Lowest unoccupied molecular orbital.

Volume 2 Issue 3 (2025) 74 doi: 10.36922/IMO025140019