Dinuclear copper(II) complexes with an unsymmetrical exchange fragment

Abstract

New dinuclear copper(II) complexes with azomethines and hydrazones, which were pro duced by condensation of substituted salicylaldehyde derivatives with 1,3 diaminopropan 2 ol or carbo(thiocarbo)hydrazide, were studied. The structures of the [Cu 2 L(µ CH 2 ClCOO)(CH 3 OH)]•(CH 3 OH) (L = C 17 H 15 N 2 O 3 ) and [Cu 2 L 2 (Cl 3 CCO)(CH 3 OH)]•H 2 O (L 2 = C 32 H 42 N 4 O 3 ) complexes were established by X ray diffraction. The magnetic properties of these complexes, including the influence of the nature of the substituents in the ligands on exchange interactions, were studied.Dinuclear copper(II) compounds with azomethine ligands and their analogs with other 3d atoms have at tracted particular attention because of their structural characteristics and magnetic properties. 1-19 The Cu II atoms contain one unpaired electron, which substan tially simplifies calculations of the energy parameters of exchange interactions. In addition, complexes with the azomethine ligand contain the stable dinuclear Cu(µ X)(µ X 1 )Cu fragment, whose geometric parameters depend only slightly on the nature of the substituents at the periphery of the molecule. This fact allows one to rather correctly estimate the exchange parameters for se ries of complexes and predict the existence of new com pounds possessing the desired magnetic properties. In this respect, compounds containing various types of X and X 1 bridges (for example, containing one and three atom bridges) are of most interest. Among these compounds are copper complexes, in which the carboxylate group serves as one of the bridging ligands (structures A and B).Investigations of such complexes containing various substituents in chelate bridging ligands and the carboxy late group provide estimates of the influence of the elec tronic and steric factors on the energetics of the spin spin exchange. However, it is important to know not only the magnetic properties but also the detailed geometry of the complexes, which requires the use of X ray diffraction. In the present study, we analyzed the magnetic data for a series of compounds of types A and B and established the structures of the key complexes. Results and DiscussionRecently, 20,21 we have developed convenient proce dures for the synthesis of a series of complexes A and B. The structure of the A type copper complex (R 1 = R 2 = H, R 3 = Me) has been established by X ray diffraction analy sis. 21 Magnetic measurements and calculations of the ex change parameters (Table 1) revealed a wide range of the -2J values for the systems under study. For complexes A,

Binuclear copper(ii) and nickel(ii) complexes based on N,N′-bis(3-formyl-5-tert-butylsalicylidene)-1,3-diaminopropan-2-ol: physicochemical and theoretical study

“…[36][37][38][39] The bond angle at the bridging methoxy oxygen atom in complex 1´ is 109.29(12), and the dihedral angle between two coordi nation planes CuO 3 N is 128.59(12). The bridging meth oxy oxygen atom shows substantial pyramidalization; the sum of the bond angles is 331.24.…”

Structure and Properties of Copper(II), Manganese(III), and Iron(III) Complexes with Potentially Pentaanionic Heptadentate Ligands Including Alkoxido, Amido, and Phenoxido Donors

“…The key factors that are usually considered to govern the nature and strength of superexchange magnetic interactions in such doubly bridged Cu II dinuclear complexes are the Cu-O alkoxido -Cu angle, the distortion from trigonalplanar toward pyramidal bonding around O alkoxido (also reflected by the dihedral angle between the copper coordination planes), and the Cu···Cu distance. [48][49][50] In 1, the Cu-O alkoxido -Cu angle is larger than in previously reported examples, [48][49][50] the bonding geometry around the alkoxido oxygen atom O3 is close to planarity, the sum of the three bond angles around O3 is 357°(small dihedral angle of 13.7°between the copper coordination planes), and the intramolecular Cu···Cu separation (3.568 Å) is at the upper end of those previously reported. [48][49][50] The values of these structural parameters support a fairly strong antiferromagnetic interaction, in agreement with the rather large |2J| value (264 cm -1 ) evaluated for 1.…”

“…[48][49][50] In 1, the Cu-O alkoxido -Cu angle is larger than in previously reported examples, [48][49][50] the bonding geometry around the alkoxido oxygen atom O3 is close to planarity, the sum of the three bond angles around O3 is 357°(small dihedral angle of 13.7°between the copper coordination planes), and the intramolecular Cu···Cu separation (3.568 Å) is at the upper end of those previously reported. [48][49][50] The values of these structural parameters support a fairly strong antiferromagnetic interaction, in agreement with the rather large |2J| value (264 cm -1 ) evaluated for 1. The magnetic susceptibility, χ M , of 2 (4) , the low-temperature paramagnetic tails are characteristic of the presence of a small percentage of paramagnetic impurity.…”

“…The parameter values for the best fit, shown as a solid line in Figure 9, are: J = -132(1) cm -1 , g = 2.024(4), p = 0.5 %. The agreement factor [48] 160-170, [49] and 96.4-173.4 cm -1 [50] ranges. The key factors that are usually considered to govern the nature and strength of superexchange magnetic interactions in such doubly bridged Cu II dinuclear complexes are the Cu-O alkoxido -Cu angle, the distortion from trigonalplanar toward pyramidal bonding around O alkoxido (also reflected by the dihedral angle between the copper coordination planes), and the Cu···Cu distance.…”

Synthesis and magnetic properties of the novel binuclear copper(II) metallochelates with unsymmetrical exchange fragment including heterocyclic derivatives

“…Lately we have synthesized the series of novel copper(II) binuclear complexes with unsymmetrical exchange fragment and studied their magnetochemical behavior [17][18][19][20][21]. The present article is devoted to the synthesis and study of type 1 binuclear complexes possessing the unsymmetrical exchange fragment also; the ligand systems being used in the synthesis of binuclear complexes are abbreviated as H 3 L (Figures 1 and 2).…”