Ferrocenyl Functional Coordination Polymers Based on Mono-, Bi-, and Heterotrinuclear organometallic Building Blocks: Syntheses, Structures, and Properties

Seven ferrocenyl functional coordination polymers with the formulas [Zn-2(mu(2)-O(2)CRFc)(4)(4,4'-bpy)](n) [(R = (CH2)(m) with m = 0 (1), 1 (2), 2 (3), 3 (4)], [ZnO2C(CH2)(4)Fc)(2)(H2O)(2)(4,4'-bpy)](n) (5), [Zn2Ca(mu(2)-O2CCH2FC)(6)center dot Zn-2(mu(2)-O(2)CCH(2)Fc)(4)(4,4'-bpy)(2)](n) (6) and [Zn2Ca(mu(2)-O2C(CH2)(2)Fc)(6)(4,4'-bpy)](n) (7) (Fc = ferrocene) have been synthesized and characterized. Single-crystal X-ray diffraction studies reveal that their one-dimensional (1-D) chain structures consist of various organometallic building blocks held together by 4,4'-bpy linkers. Polymers 1-4 are based on the paddle-wheel binuclear motif [Zn-2(O(2)CRFc)(4)]. Polymer 5 is built from the mononuclear unit [Zn(O(2)CRFc)(2)(H2O)2]. Polymer 7 is assembled by the linear heterotrinuclear cluster [Zn2Ca(O(2)CRFc)(6)] which has been rarely reported up to now. The structure of polymer 6 is a particularly fascinating I-D chain in which two kinds of building blocks ([Zn-2(O(2)CRFc)(4)] and [Zn2Ca(O(2)CRFc)(6)]) are connected alternately by 4,4'-bpy linkers. These results demonstrate that the total numbers of incorporated ferrocene moieties as well as the structures of 1-7 are closely related to the variation of metal nuclearity (from mononuclear to trinuclear) of the three kinds of organometallic building blocks. The electrochemical studies reveal a good correlation between the Fc/Fc(+) redox potentials of 1-7 and the number of methylene in ferrocenyl carboxylates.