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Cyclo- and Carbophosphazene-Supported Ligands for the Assembly of Heterometallic (Cu2+/Ca2+, Cu2+/Dy3+, Cu2+/Tb3+) Complexes: Synthesis, Structure, and Magnetism
journal contribution
posted on 2012-02-20, 00:00 authored by Vadapalli Chandrasekhar, Tapas Senapati, Atanu Dey, Sourav Das, Marguerite Kalisz, Rodolphe CléracThe carbophosphazene and cyclophosphazene hydrazides,
[{NC(N(CH3)2)}2{NP{N(CH3)NH2}2}] (1) and [N3P3(O2C12H8)2{N(CH3)NH2}2] were condensed with o-vanillin
to afford the multisite coordination ligands [{NC(N(CH3)2)}2{NP{N(CH3)NCH-C6H3-(o-OH)(m-OCH3)}2}] (2) and [{N2P2(O2C12H8)2}{NP{N(CH3)NCH-C 6H3-(o-OH)(m-OCH3)}2}] (3), respectively. These ligands were used for the preparation of heterometallic
complexes [{NC(N(CH3)2)}2{NP{N(CH3)NCH-C6H3-(o-O)(m-OCH3)}2}{CuCa(NO3)2}] (4), [{NC(N(CH3)2)}2{NP{N(CH3)NCH-C6H3-(o-O)(m-OCH3)}2}{Cu2Ca2(NO3)4}]·4H2O (5), [{NC(N(CH3)2)}2{NP{N(CH3)NCH-C6H3-(o-O)(m-OCH3)}2}{CuDy(NO3)4}]·CH3COCH3 (6), [{NP(O2C12H8)}2{NP{N(CH3)NCH-C6H3-(o-O)(m-OCH3)}2}{CuDy(NO3)3}] (7), and [{NP(O2C12H8)}2{NP{N(CH3)NCH-C6H3-(o-O)(m-OCH3)}2}{CuTb(NO3)3}] (8). The
molecular structures of these compounds reveals that the ligands 2 and 3 possess dual coordination pockets which
are used to specifically bind the transition metal ion and the alkaline
earth/lanthanide metal ion; the Cu2+/Ca2+, Cu2+/Tb3+, and Cu2+/Dy3+ pairs
in these compounds are brought together by phenoxide and methoxy oxygen
atoms. While 4, 6, 7, and 8 are dinuclear complexes, 5 is a tetranuclear
complex. Detailed magnetic properties on 6–8 reveal that these compounds show weak couplings between
the magnetic centers and magnetic anisotropy. However, the ac susceptibility
experiments did not reveal any out of phase signal suggesting that
in these compounds slow relaxation of magnetization is absent above
1.8 K.
