Synthesis and spectral characterization of bimetallic metallomacrocyclic structures [MII2-μ2-bis-{(κ2S,S-S2CN(R)C6H4)2O}] (M = Ni/Zn/Cd): density functional theory and host–guest reactivity studies

Abstract

A series of bimetallic dithiocarbamate metallomacrocyclic complexes [M^II₂-μ²-bis-{(κ²S,S-S₂CN(R)C₆H₄)₂O}]·L {R = benzyl; M = Ni^II 1, Zn^II 2, Cd^II 3; R = 1-naphthylmethyl; M = Ni^II 4, Zn^II 5, Cd^II 6 and L = Et₃N for 1, 4 only} were efficiently synthesized through a self-assembly process involving 4,4′-bis(arylmethylamino)diphenyl ethers L¹, L², CS₂ and M(OAc)₂. The compounds were characterized by micro-, relevant spectroscopic (ESI-MS, FT-IR, ¹H, ¹³C and ¹H DOSY NMR, UV-visible absorption, fluorescence) and TGA/DTA analyses. The geometry of all the complexes has been optimized by a DFT method with B3LYP/LanL2DZ basis sets. Notably, the fluorescence properties of L¹ and L² were enhanced upon complexation with Ni, Zn or Cd metal ions in the binuclear complexes 1–6. Ni^II complexes 1 and 4 gave stable residual masses of 20.1% and 29.5% in their thermogravimetric analyses which correspond to NiS (calc. 14.18% for 1 and 12.26% for 4) plus char, respectively. A Job plot experiment reveals the ability of macrocycles 1–4 to form host–guest complexes in 1 : 1, 1 : 2 and 2 : 1 stoichiometry, depending on the relative sizes of the hosts and guests and their electronic nature.