Supramolecular Interactions of Terpyridine-Derived Cores of Metallomesogen Precursors

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.

Functionalised Terpyridines and Their Metal Complexes—Solid-State Interactions

“…There is, nonetheless, only one C ... C interaction (C28...C54 i ; i = 1.5 + x, 1.5 − y, 1 + z; 3.313(3) Å) exceeding dispersion occurring between the three pairs of rings, meaning that dispersion alone is clearly the dominant factor. The complexes 28-34 all contain alkoxy-functionalised terpyridine ligands, [Fe(bzOtpy)2](ClO4)2 (28) and [Ni(bzOtpy)2](ClO4)2 (29) being additions to the fairly numerous known family [36,64,74], where the alkoxo group is attached directly to the 4′ position of 2,2′:6′,2″-terpyridine. The Hirshfeld surfaces ( Figure S4) obtained for the structures of 28 and 29 show marked differences in the number of interactions beyond dispersion, with, in particular, a complete absence of apparent C … C interactions in 29.…”

“…The Hirshfeld surfaces ( Figure S4) obtained for the structures of 28 and 29 show marked differences in the number of interactions beyond dispersion, with, in particular, a complete absence of apparent C … C interactions in 29. Such loss can be explained as arising from the nearly 200 K difference in the temperatures (28, 100 K; 29, 296 K) at which the structures were determined, with the enhanced vibrational motion at the [36,64,74], where the alkoxo group is attached directly to the 4 position of 2,2 :6 ,2terpyridine. The Hirshfeld surfaces ( Figure S4) obtained for the structures of 28 and 29 show marked differences in the number of interactions beyond dispersion, with, in particular, a complete absence of apparent C• • • C interactions in 29.…”

“…Such loss can be explained as arising from the nearly 200 K difference in the temperatures (28, 100 K; 29, 296 K) at which the structures were determined, with the enhanced vibrational motion at the higher temperature leading to some washing out of the difference between dispersion and other weak interactions. Similar differences have been observed for Co(II) complexes studied in their low-spin and high-spin forms, necessarily at quite different temperatures [37], and the Hirshfeld surface for the cation present in the structure of the Zn ( Figure S5; all for low-temperature determinations) of 28 and the Co(II) and Cu(II) complexes of the triply methoxylated ligand 4 -(1,2,3-trimethoxy-5-phenyl)-2,2 :6 ,2terpyridine, tmbzOtpy [36], shows that the introduction of the methoxyl substituents quite dramatically modifies all interactions beyond the dispersion of the cations, further supporting the contention that these interactions are generally a reflection of equilibria involving multivariate influences.…”

“…To assess the interactions within the lattices, we employed the calculation of Hirshfeld surfaces [29] using the program CrystalExplorer [30]. This work is a complement to other structural studies of functionalised terpyridines and their complexes that we have reported [14,[33][34][35][36][37] and provides results to be integrated with the present and with the extant literature in general. The ultimate objective, in general, is, of course, to use such information in the design and synthesis of functional materials [38].…”

Mesomorphism and Photophysics of Some Metallomesogens Based on Hexasubstituted 2,2′:6′, 2′′‐Terpyridines

“…It should be noted that there is a recent report of single crystal X‐ray structures of 2:1 terpy–cobalt(II) complexes, noted as “metallomesogenic precursors”, in which various intermolecular interactions were analysed in some detail.…”