The 1D coordination polymers [Cu2(syn,syn-g1:g1:l-RCOO)4(anti,anti-g1:g1:l-RCOO)(Et3NH)]n, R =Me (1) and H (2), and the dimer [Cu2(syn,syn-g1:g1:l-PhCOO)4(anti-g1-PhCOO)2(Et3NH)2] (3) are formed by reaction of copper carboxylates with the corresponding carboxylic acid and NEt3. Moreover, the compound [Cu2(syn,syn-g1:g1:l-MeCOO)4(anti-g1-MeCOO)2(Et2NH2)2] (4) can be obtained with the use of NHEt2. The crystal structures of 1 CH3CN and 2 comprise linear anionic 1D chains of paddle-wheel copper carboxylates [Cu2(RCOO)4], bridged together by anti,anti-g1:g1:l acetato or formato ions. The negative charges are balanced by hydrogen-bonded triethylammonium countercations, and in compound 1 acetonitrile molecules are hosted in the voids between the chains. In compounds 3 and 4, two anti-g1-benzoato or -acetato anions occupy the apical positions of the paddle-wheel dimers [Cu2(RCOO)4], with Et3NH+ or Et2NH2 + cations balancing the negative charges, without the formation of coordination polymer chains. In compound 4, the dimeric units are held together in a 1D network by hydrogen bonds between the apical carboxylates and the diethylammonium cations. In order to evaluate the effect of the simultaneous presence of syn,syn- and anti,anti-g1:g1:l acetato ions on the Cu–Cu magnetic communication, the magnetic susceptibility of 1 has been measured. Data were fitted to a model based on an alternating chain of copper dimers based on the Heisenberg–Zeeman Hamiltonian (-2J S1 S2 convention). The results show the presence of a strong antiferromagnetic coupling within the dimer 2J1 =-(310.8 ± 0.1) cm-1 and a weak antiferromagnetic coupling between dimers 2J2 = -(25 ± 1) cm-1. The latter coupling is sgnificant since its introduction in the fit model leads to a well-behaved error surface and to a 35% decrease of the sum of squared residuals. The electron paramagnetic resonance (EPR) spectra of powder sample of 1 have been recorded between 5 and 295 K, and they are typical of the triplet state of an antiferromagnetic copper dimer (zero field splitting |D| = 0.34 cm-1).

Copper 1D coordination polymers and dimers: Role of the carboxylate and the ammonium cation, crystal structures and magnetic studies / L. Rigamonti, S. Carlino, Y. Halibi, F. Demartin, C. Castellano, A. Ponti, R. Pievo, A. Pasini. - In: POLYHEDRON. - ISSN 0277-5387. - 53(2013), pp. 157-165. [10.1016/j.poly.2013.01.016]

Copper 1D coordination polymers and dimers: Role of the carboxylate and the ammonium cation, crystal structures and magnetic studies

L. Rigamonti
Primo
;
F. Demartin;C. Castellano;A. Pasini
Ultimo
2013

Abstract

The 1D coordination polymers [Cu2(syn,syn-g1:g1:l-RCOO)4(anti,anti-g1:g1:l-RCOO)(Et3NH)]n, R =Me (1) and H (2), and the dimer [Cu2(syn,syn-g1:g1:l-PhCOO)4(anti-g1-PhCOO)2(Et3NH)2] (3) are formed by reaction of copper carboxylates with the corresponding carboxylic acid and NEt3. Moreover, the compound [Cu2(syn,syn-g1:g1:l-MeCOO)4(anti-g1-MeCOO)2(Et2NH2)2] (4) can be obtained with the use of NHEt2. The crystal structures of 1 CH3CN and 2 comprise linear anionic 1D chains of paddle-wheel copper carboxylates [Cu2(RCOO)4], bridged together by anti,anti-g1:g1:l acetato or formato ions. The negative charges are balanced by hydrogen-bonded triethylammonium countercations, and in compound 1 acetonitrile molecules are hosted in the voids between the chains. In compounds 3 and 4, two anti-g1-benzoato or -acetato anions occupy the apical positions of the paddle-wheel dimers [Cu2(RCOO)4], with Et3NH+ or Et2NH2 + cations balancing the negative charges, without the formation of coordination polymer chains. In compound 4, the dimeric units are held together in a 1D network by hydrogen bonds between the apical carboxylates and the diethylammonium cations. In order to evaluate the effect of the simultaneous presence of syn,syn- and anti,anti-g1:g1:l acetato ions on the Cu–Cu magnetic communication, the magnetic susceptibility of 1 has been measured. Data were fitted to a model based on an alternating chain of copper dimers based on the Heisenberg–Zeeman Hamiltonian (-2J S1 S2 convention). The results show the presence of a strong antiferromagnetic coupling within the dimer 2J1 =-(310.8 ± 0.1) cm-1 and a weak antiferromagnetic coupling between dimers 2J2 = -(25 ± 1) cm-1. The latter coupling is sgnificant since its introduction in the fit model leads to a well-behaved error surface and to a 35% decrease of the sum of squared residuals. The electron paramagnetic resonance (EPR) spectra of powder sample of 1 have been recorded between 5 and 295 K, and they are typical of the triplet state of an antiferromagnetic copper dimer (zero field splitting |D| = 0.34 cm-1).
Copper carboxylates ; Paddle-wheel units ; 1D coordination polymers ; Hydrogen bond networks ; X-ray structures ; Magnetic interactions
Settore CHIM/03 - Chimica Generale e Inorganica
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/217543
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