We report here two series of coordination polymer chains: the first being [M(II)(ox)(bnz)₂]_n (M = Mn 1, Fe 2, Co 3, Ni 4, Cu 5 and Zn 6; ox = oxalate C₂O₄ ²⁻; bnz = benzimidazole) and the second [M(II)(ox)(btz)₂]_n (M = Mn 7, Fe 8, Co 9, Ni 10, Cu 11 and Zn 12; btz = benzotriazole). The first series displays an unusual homometallic [–M_i–M_ii–M_ii–]_n chain topology and the second series is isostructural to [Fe(II)(ox)(btz)₂]_n , originally reported by Jia et al. (Collect. Czech. Chem. Commun., 2002, 67, 1609–1615). These two series allow us to make comparisons between the spin state of each metal and the magnetic coupling interaction within an isostructural series spanning the full range of spin states available in 3d metals and to investigate which models are the best to use in each case. Compound 8 is a single-chain magnet, the behaviour through spin-canting arising from a Dzyaloshinskii-Moriya interaction. Additionally, we have synthesised a two-dimensional coordination polymer {[Zn(II)(bnz)₄][Zn(II)₂(ox)₃]}_n (13), in which distorted hexagonal [Zn(II)₂(ox)₃]_n ^{2n −} layers are hydrogen bonded by [Zn(II)(bnz)₄]²⁺ cations to give an interlayer separation of 12.001(2) Å.

We have demonstrated that treatment of [Fe(1)₂]²⁺ (1 = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine) with an excess of CuCl₂·2H₂O leads to competition between coordination of copper(II) by the pendant pyridine donors in [Fe(1)₂]²⁺, and transfer of ligand 1 from iron(II) to copper(II) to yield [{Cl₃Cu(µ-1)Fe(µ-1)}₂CuCl₂(OH₂)₂]Cl₂·4H₂O and [Cu(H1)Cl₂]Cl·4H₂O, respectively. Direct reaction of 1 with CuCl₂·2H₂O and variation in crystallization conditions results in the formation of either monomeric or polymeric complexes: [Cu(1)Cl₂]·4.75H₂O, [Cu(1)Cl₂]·H₂O·MeOH and [Cu(1)Cl₂·2H₂O]_n. The reaction of 1 with Cu(NO₃)₂·3H₂O gives the coordination polymer [Cu(1)(ONO₂)₂·H₂O]_n. Magnetic data for [Cu(1)Cl₂·2H₂O]_n and [Cu(1)(ONO₂)₂·H₂O]_n are consistent with antiferromagnetically-coupled chains. Reactions of CuCl₂·2H₂O with ligands 2 and 3 (2 = 4′-(3-pyridyl)-2,2′:6′,2″-terpyridine, 3 = 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine) lead to monomeric complexes. With the exception of [Cu(3)Cl₂], the mononuclear complexes show a propensity for the incorporation of water into their crystal lattices; in the case of [Cu(H1)Cl₂]Cl·4H₂O and [Cu(H1)Cl₂]Cl·4.75H₂O, the small change in water content leads to the assembly of (5.8²)₂(5.6.8)₄(5².6)₂ or (4².6²)₃(4.6²)₆water–chloride ion nets.

Dynamically porous metal-organic frameworks (MOFs) with a chiral quartz-based structure have been synthesized from the multidentate ligand 2,2′-dihydroxybiphenyl-4,4′-dicarboxylate (H₂diol). Compounds [Ni(II)(H₂diol)(S)₂]·xS (where S = DMF or DEF) show marked changes in 77 K N₂ uptake between partially desolvated [Ni(II)(H₂diol)(S)₂] (only the pore solvent is removed) and fully desolvated [Ni(II)(H₂diol)] forms. Furthermore, [Ni(II)(H₂diol)(DMF)₂] displays additional solvent-dependent porosity through the rotation of DMF molecules attached to the axial coordination sites of the Ni(II) centre. A unique feature of the four coordinate Ni(II) centre in [Ni(II)(H₂diol)] is the dynamic response to its chemical environment. Exposure of [Ni(II)(H₂diol)] to H₂O and MeOH vapour leads to coordination of both axial sites of the Ni centres and to the generation of a solvated framework, whereas exposure to EtOH, DMF, acetone, and MeCN does not lead to any change in metal coordination or structure metrics. MeOH vapour adsorption was able to be tracked by time-dependent magnetometry as the solvated and desolvated structures have different magnetic moments. Solvated and desolvated forms of the MOF show remarkable differences in their thermal expansivities; [Ni(II)(H₂diol)(DMF)₂]·DMF displays marked positive thermal expansion (PTE) in the c-axis, yet near to zero thermal expansion, between 90 and 450 K, is observed for [Ni(II)(H₂diol)]. These new MOF architectures demonstrate a dynamic structural and colourimetric response to selected adsorbates via a unique mechanism that involves a reversible change in the coordination environment of the metal centre. These coordination changes are mediated throughout the MOF by rotational mobility about the biaryl bond of the ligand.