Slight ligand modifications within multitopic linear hydroxamates promotes connectivity differences in Cu(ii) 1-D coordination polymers

Abstract

The novel multitopic ligands N-hydroxy-4-((2-hydroxy-3-methoxybenzyl)amino)benzamide (L₃H₃) and N-hydroxy-4-((2-hydroxybenzyl)amino)benzamide (L₄H₃) have been synthesised through the Schiff base coupling and subsequent reduction of 4-aminophenylhydroxamic acid and either o-vanillin (to give L₃H₃) or 2-hydroxybenzaldehyde (to give L₄H₃). These linear multitopic ligands bind Cu(II) centres at both the hydroxamate and phenol ends to form the 1-D coordination polymers [Cu(II)(L₃H₂)₂]_n (1) and {[Cu(II)(L₄H₂)₂]·2MeOH}_n (2). Slight differences in the structures of L₃H₃ and L₄H₃ lead to significant extended connectivity changes upon Cu(II) metalation that are exampled by a 27% decrease in intra-chain Cu(II)⋯Cu(II) distance upon moving from 1 to 2. The significant conformation and metal binding differences shown by L₃H₂⁻ and L₄H₂⁻ in 1 and 2 respectively have been rationalised using density functional theory (DFT) calculations. Hirshfeld surface analysis has been employed to assess and visualise the intra- and intermolecular interactions in both complexes.