Coordination Behaviour of 1-(4,2':6',4"-terpyridin-4'-yl)ferrocene and 1-(3,2':6',3"-terpyridin-4'-yl)ferrocene: Predictable and Unpredictable Assembly Algorithms*

The reaction of 1-(4,2':6',4"-terpyridin-4'-yl)ferrocene (2) with ZnI2 leads to [{ZnI2(2)}4·1.4MeOH·0.8H2O] which contains a discrete [4+4] metallocycle. Crystal growth experiments demonstrate that reactions of 2 with Zn(OAc)2 or CuCl2 result in the formation of single- or double-stranded 1D polymer chains, respectively, the latter facilitated by the formation of {Cu2Cl4} dinuclear nodes. While both 2 and its isomer 1-(3,2':6',3"-terpyridin-4'-yl)ferrocene (3) present V-shaped donor sets, rotation about interannular bonds in 3 generates flexible vectorial properties associated with limiting convergent and divergent orientations of the nitrogen donors. The synthesis and characterisation of 3 are described as are reactions of 3 with ZnCl2 or ZnBr2 which lead, respectively, to a metallosquare in [{ZnCl2(3)}4·3CHCl3·3MeOH] or a helical polymer in [{ZnBr2(3)}·MeOH]n. The tight pitch of the helix in the latter (8.7879(9) Å) is controlled by a combination of the orientations of the N,N"-donor sets in 3, and intra-chain p-stacking interactions involving ferrocenyl and pyridine units.