Molecular-programmed self-assembly of homometallic and heterometallic pentanuclear and hexanuclear coordination compounds: Synthesis, crystal structures, and magnetic properties of ladder-type (Cu2MxII)-M-II (M= Cu, Ni; x=3, 4) oxamato complexes with

摘要

New homo- and heterometallic, hexa- and pentanuclear complexes of formula {[Cu-2(mpba)(2)(H2O)F][Cu(Me(5)dien)](4)}(PF6)(3)center dot 5H(2)O (1), {[Cu-2(Me(3)mpba)(2)(H2O)(2)][Cu(Me(5)dien)](4)}(ClO4)(4)center dot 12H(2)O (2), {[Cu-2(ppba)(2)][Cu(Me(5)dien)](4)}(ClO4)(4) (3), and [Ni(cyclam)]{[Cu-2(mpba)(2)][Ni(cyclam)](3)}(ClO4)(4)center dot 6H(2)O (4) [mpba = 1,3-phenylenebis(oxamate), Me(3)mpba = 2,4,6-trimethyl-1,3-phenylenebis(oxamate), ppba = 1,4-phenylenebis(oxamate), Me(5)dien = N,N,N'N' ',N' '-pentamethyldiethylenetriamine, and cyclam = 1,4,8,11-tetraazacyclotetradecane] have been synthesized through the use of the "complex-as-ligand/complex-as-metal" strategy. The structures of 1-3 consist of cationic Cu-6(II) entities with an overall [2 x 2] ladder-type architecture which is made up of two oxamato-bridged Cu-3(II) linear units connected through two m- or p-phenylenediamidate bridges between the two central copper atoms to give a binuclear metallacyclic core of the cyclophane-type. Complex 4 consists of cationic (Cu2Ni3II)-Ni-II entities with an incomplete [2 x 2] ladder-type architecture which is made up of oxamato-bridged (CuNiII)-Ni-II and (CuNi2II)-Ni-II linear units connected through two m-phenylenediamidate bridges between the two copper atoms to give a binuclear metallacyclophane core. The magnetic properties of 1-3 and 4 have been interpreted according to their distinct "dimer-of-trimers" and "dimer-plus-trimer" structures, respectively, (H = -J(S-1A center dot S-3A + S-1A center dot S-4A + S-2B center dot S-5B + S-2B center dot S-6B) - J'S-1A center dot S-2B). Complexes 1-4 exhibit moderate to strong antiferromagnetic coupling through the oxamate bridges (-J(Cu-Cu) = 81.3-105.9 cm(-1); -J(Cu-Ni) = 111.6 cm(-1)) in the trinuclear and/or binuclear units. Within the binuclear metallacyclophane core, a weak to moderate ferromagnetic coupling (J'(Cu-Cu) = 1.7-9.0 cm(-1)) operates through the double m-phenylenediamidate bridge, while a strong antiferromagnetic coupling (J'(Cu-Cu) = -120.6 cm(-1)) is mediated by the double p-phenylenediamidate bridge.