Construction and characterization of novel molecular architectures through coordination-driven self-assembly: rhomboid and overlapped double rhomboid

Co-existence of five- and six-coordinate iron(ii) species captured in a geometrically strained spin-crossover Hofmann framework

“…[16][17][18][19][20][21][22] Additionally, angular ligands have been used to disrupt Hofmann framework formation, such as in [Fe II (H 2 O) 2 Fe II (DPSe) 2 (Pt(CN) 4 ) 2 ]•3EtOH (4,4′-dipyridylselenide), which contains two types of six-coordinate Fe II sites, one SCO-active the other remaining high spin (HS). 23 Here, by incorporating a relatively more rigid, yet still angular ligand into a Hofmann-type framework (4,2′:6′,4′′-terpyridine (TPy); Scheme 1a), 24 we report a framework that shows several signatures of extreme geometric frustration, including: metal binding by only one end of the ligand and consequently 2-D rather than 3-D Hofmann framework formation, and the presence of two Fe II sites with distinct coordination numbers (Scheme 1b), one being SCO-active and the other persistently HS. Notably, the SCO-inactive site is a rare five-coordinate Fe II species, [25][26][27][28][29] the local stability of which appears to be enhanced by geometric requirements of the framework lattice and hydrogen bonding interactions.…”