Thermal and Light‐Induced Spin Transitions of Fe^II Complexes with 4‐ and 5‐(Phenylazo)‐2,2′‐bipyridine Ligands: Intra‐ vs. Intermolecular Effects

Abstract

Five new spin crossover complexes with 4-and 5-(phenylazo)-2,2-bipyridine (4-/5-PAbipy) ligands were synthesized and investigated with respect to their spin crossover (SCO) behavior. The results are compared to the thermal and lightinduced spin transition properties of the parent SCO complexes [Fe(bpz) 2 (bipy)] (1) and [Fe(bipy) 2 (NCS) 2 ] (2). [Fe(bpz) 2 (4-PAbipy)] (1a) undergoes a stepwise spin transition whereas [Fe(bpz) 2 (5-PAbipy)] (1b) exhibits a one-step transition with a 6 K-wide hysteresis. For [Fe(bpz) 2 ( tBu 5-PAbipy)] (1c) the spin [a]

Light-Induced Spin Crossover in an Fe(II) Low-Spin Complex Enabled by Surface Adsorption

“…This light source is adequate for LIESST experiments on typical SCO complexes. 68 Diamagnetic corrections were applied using the tabulated Pascal's constants.…”

A photoresponsive palladium complex of an azopyridyl-triazole ligand: light-controlled solubility drives catalytic activity in the Suzuki coupling reaction

“…The first step of the synthesis was a Mills reaction between 5-amino-2-bromo-pyridine and nitrosobenzene affording 2-bromo-5-(phenylazo)pyridine 1. 30 A subsequent Sonogashira coupling between 1 and TMS-acetylene followed by the deprotection of alkyne 2 yielded compound 3. The terminal alkyne of compound 3 was transformed into triazole rings via azide–alkyne cycloadditions with benzyl azide and hexyl azide leading to ligands 4 and 5, respectively (for detailed synthetic procedures, see ESI † ).…”

Structural movies of the gradual spin-crossover in a molecular complex at various physical scales

“…19,20,[30][31][32] It is not less known that, conversely, the geometry of the HS coordination sphere influences some of the SCO features. [18][19][20][21][22][23][24][25][33][34][35][36][37] From HS to LS, the Fe-N bond lengths decrease by an average value of 0.2 Å, the latter considerably varying depending on the concerned ligands, and the FeN 6 octahedron is more regular in the LS state. The metal ion sphere volume strongly decreases at the HS -LS SCO and conversely.…”