A new zinc(II) trinuclear heteroleptic coordination compound derived from zinc acetate and N-salicylidenecyclohexylamine

Abstract

We report on a one-pot reaction of a mixture of cyclohexylamine and salicylaldehyde with a half of equivalent of Zn(OAc)₂ in EtOH, which allowed to produce a novel discrete trinuclear heteroleptic complex [Zn₃L₂(OAc)₄] (1), where L is a monodeprotonated anion of N-cyclohexylsalicylideneimine (HL). Notably, our numerous attempts to produce the previously reported discrete mononuclear homoleptic complex [ZnL₂] using both the reported and a series of the modified by us synthetic approaches failed, and complex 1 was the exclusively isolated product. These findings cannot be explained at the moment. The molecular structure of 1 is centrosymmetric and comprises a trinuclear central Zn₃⁶⁺ cationic backbone. The terminal metal cations are coordinated by the imine nitrogen atom and phenolate oxygen atoms of one ligand L, and by two oxygen atoms of two acetate anions, yielding a distorted NO₃ tetrahedral coordination environment. The central metal cation is coordinated by two phenolate oxygen atoms from two ligands L and by four oxygen atoms of four acetate anions, yielding a slightly distorted O₆ coordination environment. Thus, both the L and acetate anions in the structure of 1 serve as bridging ligands linking two Zn²⁺ cations. The crystal packing of 1 was studied in detail by the Hirshfeld surface analysis. A solution of 1 in DMSO absorbs from 250 nm to about 420 nm with two clearly defined bands centered at 273 and 368 nm due to intraligand transitions within L and the acetate anions. The DFT-based calculations were also applied to shed light on the structural and optical features of 1. A molecular docking approach revealed that 1 can potentially inhibit hemoglobin S with the so-called ligand efficiency scores being within the recommended ranges for a drug, although some parameters are slightly out of the recommended ranges.