Linking chiral clusters with molybdate building blocks: from homochiral helical supramolecular arrays to coordination helices.
The synthesis of four new oxo-centered Fe clusters (1 a-c, 2) of the form [Fe(III)3(mu3-O)(CH2=CHCOO)6] with acrylate as the bridging ligand gives rise to potentially intrinsically chiral oxo-centered {M3} trimers that show a tendency to spontaneously resolve upon crystallization. For instance, 1 a, [Fe(III)3(mu3-O)(CH2=CHCOO)6-(H2O)3]+, crystallizes in the chiral space group P3(1) as a chloride salt. Crystallization of 1 b, [Fe3(mu3-O)(C2H3CO2)6(H2O)3]NO3 x 4.5 H2O, from aqueous solution followed by recrystallization from acetonitrile also gives rise to spontaneous resolution to yield the homochiral salt [Fe3(mu3-O)(C2H3CO2)6-(H2O)3]NO3 x CH3CN of 1 c (space group P2(1)2(1)2(1)). Furthermore, the reaction of 1 a with hexamolybdate in acetonitrile gives the helical coordination polymer {[(Fe3(mu3-O)L6(H2O))(MoO4)-(Fe3(mu3-O)L6(H2O)2)] x 2 CH3CN x H2O}infinity 2 (L: H2C=CHCOO), which crystallizes in the space group P2(1). The nature of the ligand geometry allows the formation of atropisomers in both the discrete (1 a-c) and linked {Fe3} clusters (2), which is described along with a magnetic analysis of 1 a and 2.
Long
De-Liang
DL
WestCHEM, Department of Chemistry, The University of Glasgow, Glasgow, G12 8QQ, UK.
Kögerler
Paul
P
Farrugia
Louis J
LJ
Cronin
Leroy
L