An organometallic complex revealing an unexpected, reversible, temperature induced SC–SC transformation†
A reversible, temperature driven phase transformation that takes place at ca. 180 K, in a single-crystal to single-crystal manner, has been observed for a monometallic transition metal coordination complex based on a fac-Re(CO)3 core, with a chelated 2,2′-bipyridine unit and a halogenated N-(4-iodophenyl)nicotinamide axial co-ligand. A range of closely related analogues that varied the halogen and its position of substitution exemplified the rarity of such an observation: none of the eight structurally related examples demonstrated such interesting behavior in the temperature range of study. The structures of all the complexes also revealed that the trifluoromethanesulfonate counter anion plays an important role through hydrogen bonding, but no isomorphism or polymorphism was observed. The complexes are also fully characterised from a spectroscopic perspective, with IR, UV-vis, time-resolved luminescence and NMR spectroscopies providing complementary solution-state data.