Solvent influence on the crystal structures of new cadmium tri-tert-butoxysilanethiolate complexes with 1,4-bis(3-aminopropyl)piperazine: luminescence and antifungal activity.

Abstract

Monocrystals of dinuclear μ-1,4-bis(3-aminopropyl)piperazine-κ⁴N¹,N^1':N⁴,N^4'-bis[bis(tri-tert-butoxysilanethiolato-κS)cadmium(II)], [Cd₂(C₁₂H₂₇O₃SSi)₄(C₁₀H₂₄N₄)] or [Cd₂{SSi(OtBu)₃}₄(μ-BAPP)], 1, and polynuclear catena-poly[[bis(tri-tert-butoxysilanethiolato-κS)cadmium(II)]-μ-1,4-bis(3-aminopropyl)piperazine-κ²N^1':N^4'], [Cd(C₁₂H₂₇O₃SSi)₂(C₁₀H₂₄N₄)]_n or [Cd{SSi(OtBu)₃}₂(μ-BAPP)]_n, 2, with 1,4-bis(3-aminopropyl)piperazine (BAPP) and tri-tert-butoxysilanethiolate ligands, were obtained from the same ratio of reactants, but with different solvents used for the crystallization processes. The structures and properties of both complexes were characterized using elemental analysis, X-ray diffraction and FT-IR, ¹H NMR and luminescence spectroscopy. Applied density functional theory (DFT) computational methods and noncovalent interaction (NCI) analysis were used for geometry optimization and visualization of the interactions between the metallic centres and their surroundings. The X-ray analysis revealed four-coordinate Cd^II centres bound to two S atoms of the silanethiolate groups and two N atoms of the BAPP ligand; however, it chelates to tertiary and primary N atoms in 1, whilst in 2 it does not chelate and bonds only to RNH₂. The photoluminescence properties of complexes 1 and 2 result from free-ligand emission and differ significantly from each other with respect to emission intensity. Additionally, antifungal activity was investigated against 18 isolates of fungi. Compound 1 strongly inhibited the growth of three dermatophytes: Epidermophyton floccosum, Microsporum canis and Trichophyton rubrum.