The rational design of novel platinum complexes has become a requirement in the modern world due to emergence of adverse effects and resistance in cisplatin and related drugs. In this study, two novel platinum (II) complexes [Pt(N(SO2)(bzd)dpa)Cl2] (C1) and [Pt(N(SO2)(4-Mebip)dpa)Cl2] (C2) of two novel dipicolylamine appended ligands N(SO2)(bzd)dpa (L1) and N(SO2)(4-Mebip)dpa (L2) were synthesized in good yield and high purity. Formation of ligands and metal complexes were confirmed by single crystal X-ray diffraction and 1H NMR spectroscopy and characterized by other spectroscopic techniques (UV–Vis, FTIR and fluorescence). Interestingly, L1 has two conformations since the dioxan ring exists with the occupancy ratio of 95:5 in solid state whereas C1 is devoid of such conformations may be due to ring rigidity upon complexation which can be further confirmed by S-N bond length of C1 (1.6303 Å) which is lower than in L1 (1.6434 Å). In contrast, L2 ligand crystal undergoes phase transition to triclinic form with twinning at 90 K whereas, at 150 K the ligand exists in monoclinic system; populations of the two orientation for one pyridine substituent are about 78:22. C2 was observed with no phase transition at 90 K may be due to stability with metal coordination to ligand. The methylene protons of L1 and L2 appears as a singlet at 4.50 ppm and 4.57 ppm in 1H NMR spectra and their corresponding complexes observed as two doublets (5.91 ppm and 5.25 ppm, 6.02 ppm and 5.29 ppm) in DMSO-d6. The absorption peaks (200-300 nm) in UV-Vis spectra can be assigned to intra-ligand π→π* and n→π* transitions. In FTIR spectra of L1, L2 ligands, the peaks at 917 cm-1 and 920 cm-1 are due to S-N stretching vibrations, have shifted to 914 cm-1 (C1) and 925 cm-1 (C2). Emission spectra were recorded for both ligands; L1, L2 showed intense fluorescence properties at 330 nm (in acetonitrile) and 370 nm (in methanol) while Pt complexes showed lower intensities than the respective ligands. Biological target predictions were explored for the two ligands by using “SwissTargetPrediction” and “SwissADME” servers; none of them violate the Lipinski rule of five. Phosphodiesterase 10A was discovered as the highest target probability for both ligands which may be potential drugleads for neurological and psychiatric disorders.

Synthesis, characterization, crystal structures of novel di-(2-picolyl) amine appended rigid phenyl based and non-rigid 1,4-benzodioxan based ring systems and their Pt (II) complexes towards potential biological applications

ACS Spring Meeting 2021

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