Optical properties, structural, and DFT studies of Pd(II) complexes with 1‐phenyl‐1H‐tetrazol‐5‐thiol, X‐ray crystal structure of [Pd(κ1‐S‐ptt)2(κ2‐dppe)] complex

Abstract

Seven tetrazole‐thione complexes, [Pd2(κ2‐ptt)4](1), trans‐[Pd(k1‐S‐ptt)2(PPh3)2] (2), trans‐[Pd(k1‐S‐ptt)2(SPPh3)2] (3), trans‐[Pd(k1‐S‐ptt)2(OPPh3)2] (4), [Pd(k1‐N‐ptt)2(k2‐dppe)] (5a), [Pd(k1‐S‐ptt)2(k2‐dppe)] (5b), [Pd(k1‐S‐ptt)2(k2‐dppeS2)] (6), and [Pd(k1‐S‐ptt)2(k2‐dppeO2)] (7), were prepared from 1‐phenyl‐1H‐tetrazole‐5‐thiol (Hptt), with substituted phosphines. These complexes were investigated by CHNS analysis; infrared (IR), nuclear magnetic resonance (NMR) (1H and 31P), and ultraviolet–visible (UV–Vis) spectroscopy; and single‐crystal X‐ray data for 5b. In Complex 1, the ptt− ligand adopted μ2‐ k‐N, k‐S bridging mode to afford a dimeric complex, whereas in Complexes 2–4, 6, and 7, the ptt− was covalently coordinated via sulfur atom of the thiol group as a solo product. In contrast, in Complex 5, the ptt− ligand was bonded in a monodentate fashion through a deprotonated tetrazole ring nitrogen atom in isomer 5a or via a thiolato sulfur atom in isomer 5b. These linkage isomers were clearly shown in the 31P‐{1H} NMR. To explain the adoption of the ligand binding modes in Complexes 5a and 5b, geometry optimization calculations were carried out on two isomers. Very small differences of all molecular parameters were found between 5a and 5b isomers. This confirms the reason for obtaining two isomers. Also, theoretical studies are made for all compounds, and excellent agreement is obtained with experimental data. The direct band gap (Eg) values are equal to 2.88, 2.85, and 2.45 eV for Complexes 1, 2, and 4, respectively, revealing a semiconductor nature. The inhibition activity of Complexes 1–3, 5, and 8 were evaluated versus the growth of four types of bacteria in vitro. The complexes showed a good activity compared with free ligand and a standard antibiotic.