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Spin Crossover in [Fe(qsal-5-Brq)2]+ Complexes with a Quinoline-Substituted Qsal Ligand
Feng-Li Chen1, Yu-Chen Sun1, Xin-Li Liu1
1State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China.
Abstract:
Using a quinoline substituted Qsal ligand, Hqsal-5-Brq (Hqsal-5-Brq = N-(5-bromo-8-quinolyl)salicylaldimine), four FeIII complexes, [Fe(qsal-5-Brq)2]A·CH3OH (Y = NO3- (1), BF4- (2), PF6- (3), OTf- (4), were prepared and characterized. Structure analysis revealed that complex 2 contained two species (2(P1̅) and 2(C2/c)). In these compounds except 3, the [Fe(qsal-5-Brq)2]+ cations form 1D chains through π-π interactions and other weak interactions. Adjacent chains are connected to form the 2D "Chain Layer" structures and 3D structures through various supramolecular interactions. For 3, a "Dimer Chain" structure is formed from the loosely connected dimers. Magnetic studies revealed that compounds 1 and 2(P1̅) displayed abrupt hysteretic SCO with the transition temperature T1/2↓ = 235 K, T1/2↑ = 240 K for 1 and T1/2↓ = 230 K, T1/2↑ = 235 K for 2(P1̅), while compounds 3 and 4 are in the HS state. Desolvation of the complexes significantly modifies their SCO properties: the desolvated 1 and 2 show a gradual SCO, desolvated 3 undergoes a two-step SCO, and desolvated 4 exhibits a hysteretic transition. Overall, this work reported the FeIII-SCO complexes of the quinoline-substituted Hqsal ligand and highlighted the potential of these ligands for the development of interesting FeIII-SCO materials.
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