| Fe/Co Prussian blue analogues?PBAs?have attracted continuous attention in recent yaers due to their tunable optical and magnetic behaviors associated with thermally and optically induced electron transfer between the FeLS?-CN-CoLS??LS=low spin?linkages and FeLS?-CN-CoHS? linkages?HS=high spin?.A series of zero dimensional model clusters were designed and constructed through brick and mortar building block methods to further investigate the magneto-structural correlation.The charge transfer behavior was found to be sensitive to the the redox potentials of metal centers,which can be affected by the coordination environment of metal centers,intermolecular interactions?hydrogen bonds and?-?stacking?and the lattice solvents.However,there are still many challenges to be addressed,such as how to regulate the transition temperature and rate of thermal induced electron transfer precisely;how to stabilize and increase the lifetime of the light-induced excited state;how to achieve the multi-step charge transfer behavior or introduce another functionality into this system.We are focusing on a new project based on the well-known[Fe2Co2]square system by introducing convenient functional groups,such as aldehyde group,into 2,2?-bipyridine(4-formyl-4?-methyl-2,2?-bipyridine,bpyCHO),which may further react with amines:A series of[Fe2Co2]square complexes({[?Tp*?Fe?CN?3Co(bpyCHO)2]2[ClO4]2}×2CH3CN×H2O?1?,{[?Tp*?Fe?CN?3Co(bpyC=NMe)2]2[ClO4]2}×2CH3CN×2H2O?2?,[?Tp*?Fe?CN?3Co(bpyC=N?n-Pr?)2]2[ClO4]2?3?,[?Tp*?Fe?CN?3Co(bpyC=N?i-Pr?)2]2[ClO4]2?4?,[?Tp*?Fe?CN?3Co(bpyC=N?n-Bu?)2]2[ClO4]2?5?)were synthesized based on the bipyridine derivatives(bpyC=NR)obtained by the simple Schiff base reaction between bpyCHO and monoamines(NH2CnH2n+1,n=1-4).No electron transfer behavior is observed in compound 1,while the methylamine-modified complex 2 has partial electron transfer.A series of novel[Fe2Co2]square complexes?Capsule?({[?Tp*?Fe?CN?3Co(bpy2N5)2]2[ClO4]2}×6DMF?6?,{[?Tp*?Fe?CN?3Co(bpy2N7)2]2[ClO4]2}×6DMF?7?,{[(Tp3,Me)Fe?CN?3Co(bpy2N7)2]2[ClO4]2}×8DMF?8?,{[(Tp3,Me)Fe?CN?3Co(bpy2N9)2]2[ClO4]2}×2MeCN×2Et2O×2H2O?9?,{[?Tp*?Fe?CN?3Co(bpy2N11)2]2[ClO4]2}×5MeCN?10?)were obtained in a similar way to complexes 1-5,by using the diamine bipyridine derivatives(bpyC=N?CH2?nN=Cbpy).Magnetic studies indicated distinct charge transfer behavior for 6-10.Specifically,complex 8 has a full electron transfer and T1/2 is about 316 K,while complexes 6,9 and 10 exhibit partial electron transfer behavior.A two-step electron transfer behavior was observed for complex 7.Variable-temperature single-crystal diffractions were further measured,which were in consistent with the magnetic analysis. |
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