Abstract
Use of Hirshfeld surfaces calculated from crystal structure determinations on various transition metal ion complexes of three terpyridine ligands carrying trimethoxyphenyl substituents has enabled an assessment of the contribution made by the ligand components to the interactions determining the lattice structures, interactions expected also to be present in metallomesogens derived from similar ligands. The form of the link joining the trimethoxyphenyl substituent to the 4′ position of 2,2′;6′,2″-terpyridine is of some importance. In the case of the Co(II) complexes of two of the ligands, their spin-crossover characteristics can be rationalised in terms of the different interactions seen in their lattices.
Highlights
The effectiveness of 2, 2,2';6',2''-terpyridine as a ligand and the variety of functionality which may be introduced through substitution on this core [1] have engendered intense interest in the coordination chemistry and possible applications of this ligand and its derivatives [2]
In [Co(L1)2 ](BF4 )2 ∙CH3 CN∙0.5H2 O, the primary role of cation–anion interactions is indicated by the fact that the lattice contains chains of cations separated by a (9.5623(3) Å), the shortest Co...Co separation in the lattice, with the cations linked as a result of interactions (CH...F and F...π but see ahead) with both anions and certainly not as a result of terpyridine embraces, unlike unsubstituted terpyridine systems where the shortest cation separations are almost always associated with such embraces [8,9,11]
For all complexes other than [Fe(L1)2 ](ClO 4 )2 ∙CH3 CN, crystals were coated with Paratone-N oil and the diffraction data measured at temperatures between 100 and 294 K depending on the particular species with synchrotron radiation (λ in the range 0.62988–0.85000 Å depending on the crystal) on an ADSC Quantum-210 detector at 2D SMC with a silicon (111) double crystal monochromator (DCM)
Summary
The effectiveness of 2, 2,2';6',2''-terpyridine as a ligand and the variety of functionality which may be introduced through substitution on this core [1] have engendered intense interest in the coordination chemistry and possible applications of this ligand and its derivatives [2] One aspect of this chemistry which has been a particular concern of the present authors and their collaborators is the induction of mesomorphic behaviour in Co(II) and Fe(II) complexes as a means of controlling their magnetic properties involving “spin crossover” [3,4]. It has been shown that the Co(II) complex of ligand L1 (Figure 1; R = C 16 H33 ), for example, undergoes a high-spin to low-spin change in magnetism which is triggered by a crystal- to-mesophase transition [5] In this case, as in many others, [6] the introduction of a gallate- like substituent with three hexadecyloxy groups at the 4'. The nature of the link between the terpyridine and trimethoxyphenyl units has proven to be of some significance
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