Pseudohalide coligands guided structural motifs, magnetism and BSA-interactions of copper(II) complexes derived from 1,3-dimethy-6-aminouracil

Abstract

Two novel copper(II) complexes with mononuclear (1) and 1D polynuclear (2) structural motifs were synthesized using the novel planar tridentate ligand 1,3-dimethyl-5-(thiazolyl-azo)-6-aminouracil, H2L (triclinic, PĪ space group and Z = 2) and pseudohalide coligands, namely azido and thiocyanato ligands. 1 is a monomeric-azo-azido complex with the monoclinic crystal system and P21/n space group, whereas 2 is a 1D polynuclear coordination polymer of Cu(II)-azo-µ-SCN (µ-SCN is bonded in the end-to-end (anti mode) manner) with the orthorhombic crystal system and Pbca space group. The crystallographic study, magneto-structural study and EPR spectra revealed distinctly that both complexes possess a slightly distorted square-pyramidal geometry about the Cu(II) ion. The observed and/or theoretical TDDFT bands show the nature of multiple intraligand, ligand-to-metal, metal-to-ligand charge transfer and d-d transitions. Direct current (dc) variable-temperature magnetic susceptibility measurements on polycrystalline samples of 1 and 2 were carried out in the temperature range 1.8–300 K. The copper(II) ions remain non-interacting at 300 K (χmT: 0.417 cm3 mol−1 K for 1 and 0.361 cm3 mol−1 K for 2). The Weiss constant for 1 is −2.3 K and for 2 it is 0.96 K, indicating that weak antiferromagnetic and weak ferromagnetic interactions exist in 1 and 2, respectively. As expected, complex 1 exhibits an intermolecular type of interaction (zJ′ = −1.37(1) cm−1), whereas 2 exhibits an intramolecular magnetic interaction (J = 1.17(2) cm−1) between the Cu(II) ions. The cause of the weak ferromagnetic coupling in 2 may be due to the orthogonality of the magnetic orbitals (dx2-y2) involved in the equatorial-axial singly bridging SCN moiety. All the compounds show excellent binding interactions (KA) with BSA, with the order complex 1 (1.993 × 104 M−1) > complex 2 (6.072 × 103 M−1) > free ligand (2.619 × 103 M−1).