Not just size and shape: spherically symmetrical d5 and d10 metal ions give different coordination nets with 4,2′:6′,4″-terpyridines

Abstract

Functionalized 4,2′:6′,4″-terpyridine ligands have been used to provide a divergent N,N′-donor set for the formation of coordination polymers containing {Zn₂(µ-OAc)₄} or {Mn₃(µ-OAc)₄(OAc)₂} scaffolds. Single-stranded coordination polymers are produced from the reactions of 4′-(4-bromophenyl)-4,2′:6′,4″-terpyridine (1) and 4′-(4-methylthiophenyl)-4,2′:6′,4″-terpyridine (2) with Zn(OAc)₂·2H₂O. In [Zn₂(1)(OAc)₄]_n and [Zn₂(2)(OAc)₄]_n, the two outer nitrogen donors of the 4,2′:6′,4″-terpyridine ligands, bind to the axial sites of {Zn₂(µ-OAc)₄} units to generate coordination polymer chains which are π-stacked so that the V-shaped ligand domains are interleaved. When Mn(OAc)₂·4H₂O is treated with 4′-(4-bromophenyl)-4,2′:6′,4″-terpyridine, the triply stranded coordination polymer {[Mn₃(1)₃(OAc)₆]·0.8MeOH·2.2H₂O}_n assembles in which the 4,2′:6′,4″-terpyridine ligands span between {Mn₃(µ-OAc)₄(OAc)₂} units. Efficient face-to-face π-interactions between pairs of pyridine rings or pairs of bromophenyl rings are the dominant packing forces. The magnetic properties in {[Mn₃(1)₃(OAc)₆]·0.8MeOH·2.2H₂O}_n are dominated by the presence of a weak antiferromagnetic interaction between the central Mn(II) ion and the two lateral ones within the linear trimeric unit, leading to an S = 5/2 ground state.