Protonated 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine and its Fe(II) bischelates: Syntheses and molecular structures

Compounds of the molecular formulae, [LH3](NO3)3 (1), [Fe(LH)2](PF6)4·5H2O (2), [Fe(L)2][Fe(L)(LH)](PF6)5·H2O (3), [Fe(L)2][Fe(L)(LH)](BF4)5·2H2O (4) and [Fe(L)2](Cr2O7)·6H2O (5) have been synthesized using 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine (L). The molecular structures of all the compounds were determined. The Fe(II) complexes are high spin in nature at room temperature and upon cooling a gradual spin-transition is observed. Among 1–5, hydrogen-bonding, π···π, and anion···π interactions as well as water tetramer and pentamer are present in the molecular packing.