Abstract

A new sterically bulky Schiff base ligand, N-(8-quinolyl)-5-tert-butylsalicylaldimine (Hqsal-5-tBu) has been prepared and a series of Fe^III complexes, [Fe(qsal-5-tBu)<inf>2</inf>]Y (Y = Cl 1, ClO<inf>4</inf> 2, NO<inf>3</inf> 3, BF<inf>4</inf> 4) utilising this ligand are reported and fully characterised. UV-vis spectroscopic and electrochemical studies indicate that 1-4 are high spin (HS) in solution at room temperature and further suggest that the tBu group only slightly alters the electronic properties of 1-4 compared with related [Fe(qsal-5-X)<inf>2</inf>]⁺ systems. The structures of [Fe(qsal-5-tBu)<inf>2</inf>]Cl·4MeOH·H<inf>2</inf>O 1, [Fe(qsal-5-tBu)<inf>2</inf>]ClO<inf>4</inf>·MeOH 2, and [Fe(qsal-5-tBu)<inf>2</inf>]NO<inf>3</inf> 3 determined at 100K reveal HS Fe^III centres in all cases. Four-fold parallel aryl embraces and π-π interactions serve to link the cations forming 2D sheets mirroring the motifs found in other [Fe(qsal-5-X)<inf>2</inf>]⁺ complexes. Despite this the tBu group causes strong distortions at the Fe centre which as magnetic studies reveal prevent spin crossover trapping 1-4 in the HS state.