Towards rational design of zinc(ii) and cadmium(ii) sulfonate-arsonates with low dimensional aggregations

Abstract

Hydrothermal reactions of zinc(II) or cadmium(II) salts with o-sulfophenylarsonic acid (o-HO₃S-C₆H₄-AsO₃H₂, H₃L) afforded two layered compounds, namely, [Zn₂(L)(OH)(H₂O)]·H₂O (1) and [Cd₃(L)₂(H₂O)₃]·H₂O (2). Introduction of 2,2′-bipyridine (bipy), 1,10-phenanthroline (phen), and 2,2′:6′,2′′-terpyridine (terpy) as auxiliary chelating ligands led to a series of zinc(II) or cadmium(II) sulfonate-arsonates with lower dimensional aggregations, namely, [Zn(HL)(bipy)₂]₂·6H₂O (3), [Cd(HL)(bipy)]₂ (4), [Zn(HL)(phen)]₂·2H₂O (5), [Cd(HL)(phen)(H₂O)]₂[Cd(HL)(phen)]₂ (6), [Cd(HL)(phen)]₂·2H₂O (7), [Zn(HL)(terpy)]₂ (8), [Cd(HL)(terpy)]₂·2H₂O (9), Zn(HL)(bipy) (10), Zn(HL)(bipy)·2H₂O (11), and Zn(HL)(phen)·H₂O (12). Compound 3 contains two mononuclear cluster units, whereas 4–9 feature five types of dinuclear cluster units in which a pair of Zn²⁺ or Cd²⁺ ions are interconnected by two sulfonate-arsonate ligands (via M–O–M, M–O–As–O–M and M–O–S–O–M bridges). Compounds 10 and 11 feature a one-dimensional (1D) chain in which each pair of Zn²⁺ centers are bridged by one arsonate group of a sulfonate-arsonate ligand. In compound 12, dinuclear clusters and 1D chains coexist. All twelve compounds display very strong fluorescence in the ultraviolet or blue light region.