One pot synthesis of two potent Ag(I) complexes with quinoxaline ligand: X- ray structure, Hirshfeld analysis, antimicrobial, and antitumor investigations

Abstract In one pot, the self-assembly of Ag(I) nitrate and 2-chloroquinoxaline (2Cl-quinox) in water-ethanol mixture afforded two novel crystalline Ag(I) complexes. The major product is the polymeric complex [Ag(2Cl-quinox)(NO3)]n; (1) while the minor product (2) comprised two complex molecules which are the monomeric [Ag(2Cl-quinox)2(NO3)]; (2a) and polymeric [Ag(2Cl-quinox)(NO3)]n; (2b) complexes. The single crystal X-ray structure revealed that 1 and 2b are made up of two-dimensional infinite sheets. In contrast, 2a is a monomeric complex which has a highly distorted tetrahedral geometry around Ag(I) center. In all cases, the 2Cl-quinox molecule acts as a terminal monodentate ligand. Using Hirshfeld surface analysis, it is found that the complex units 1 and 2b not only have very similar molecular structures but also have almost similar crystal packing. The O...H hydrogen bonds and π-π stacking interactions contributed significantly to the molecular packing. Both complexes have broad-spectrum action towards multi drug-resistance (MDR) bacteria. The most effective function of 2 is against Proteus morganii with a MIC value of 8 µg/mL. Complex 2 (IC50 = 5.93 ± 0.52 𝜇g/mL) has remarkably greater cytotoxic effect towards lung carcinoma (A-549) than cis-platin (IC50 = 7.5 ± 0.69 𝜇g/mL) and AgNO3 (IC50 = 14.7 ± 0.53 𝜇g/mL). The cytotoxicity of complex 2 towards lung (A-549) and breast (MCF-7) cancer cell lines is greater than that of 1. This might be attributed to the higher content of silver in complex 2 than 1.