Exchange interactions in a one-dimensional bromo-bridged copper(II) compound with a ladder-like structure

A deep green complex, [Cu(L)(μ-Br)Br]2 (L = 1,4-diazacycloheptane) was synthesized and its crystal structure and magnetic properties have been studied. The structure determination reveals that in the binuclear unit each copper(II) occupies a distorted square pyramidal geometry in which each bridging bromine atom is simultaneously ligated in axial and equatorial positions between two adjacent copper(II) centres. The binuclear units are packed along the [101] direction. Each dimer is connected to its two nearest neighbours by two Cu–(μ-Br)⋯H–N–Cu hydrogen bonding interactions resulting in an infinite 1D ladder-like chain. The magnetic data were fitted considering the interdimer interactions using different models to obtain precise results and the susceptibility vs. temperature curve for the complex exhibits a maximum at 12 K indicating antiferromagnetic behaviour. Magneto-structural correlations have also been carried out.

[1]  T. Maji,et al.  The first structurally alternating copper(II) chain with alternate single end-on and end-to-end azido bridging: a synthesis, crystal structure, and low-temperature magnetic study. , 2000, Inorganic chemistry.

[2]  M. James,et al.  Synthesis and crystal structure of the 1-dimensional dihalide-bridged polymers: dichlorobis(thiazole)iron(II) and dibromobis(thiazole)copper(II) , 1998 .

[3]  Louis J. Farrugia,et al.  ORTEP-3 for Windows - a version of ORTEP-III with a Graphical User Interface (GUI) , 1997 .

[4]  M. V. Rajasekharan,et al.  Synthesis, Crystal Structure, Magnetic Properties, and EPR of Cu(bp3ca)Br(2).H(2)O (bp3ca = 2,2'-Bipyridine-3,3'-dicarboxylic Acid). Ferromagnetic Interactions via Unsymmetrical Bromide Bridges. , 1997, Inorganic chemistry.

[5]  W. Robinson,et al.  Crystal chemistry of the copper bromide/2-aminopyrimidine system , 1997 .

[6]  J. M. Salas,et al.  Structural and Magnetic studies on a Bromine-Bridged Copper(II) Dimer with 5,7-Dimethyl[1,2,4]triazolo[1,5-a]pyrimidine , 1994 .

[7]  R. Caballol,et al.  Structural dependence of the singlet-triplet gap in doubly bridged copper dimers: a variational CI calculation , 1994 .

[8]  J. Bridson,et al.  Dinuclear copper(II) complexes of the tetradentate thiadiazole ligands BPMTD (2,5-bis((2-pyridylmethyl)thio)thiadiazole) and BPTD (2,5-bis(2-pyridylthio)thiadiazole). X-ray structures of [Cu2(BPTD)(.mu.2-Br)2Br2] and [Cu(BPMTD)Cl2]n and spectroscopic, electrochemical, and magnetic studies , 1994 .

[9]  G. Fallon,et al.  The molecular structures and magnetic properties of μ3-tetranuclear β-diketonate copper complexes [Cu(bzac)(μ3-OC2H4OCH3)]4 and [Cu(μ-dbm)(μ3-OC2H4OCH3)]4 , 1993 .

[10]  D. Gatteschi,et al.  MAGNETIC PROPERTIES OF HIGH NUCLEARITY SPIN CLUSTERS. A FAST AND EFFICIENTPROCEDURE FOR THE CALCULATION OF THE ENERGY LEVELS , 1993 .

[11]  T. Tarantelli,et al.  Exchange interaction in multinuclear transition metal complexes. 14. Exchange interactions in a novel copper(II) linear-chain compound with ladderlike structure: Cu2(1,4-diazacycloheptane)2Cl4 , 1990 .

[12]  B. Scott,et al.  Structural and magnetic properties of dimorpholinium hexahalodicuprate(II) salts: study of two planar Cu2X62− dimers , 1988 .

[13]  R. Willett,et al.  Magnetic and structural correlations in bis(aminopyridinium) hexachlorodicuprate and hexabromodicuprate dihydrate , 1988 .

[14]  B. Scott,et al.  Structural and magnetic properties of bis(ethanolammonium)hexahalodicuprate(II) salts: Copper(II) halide dimers with a square-pyramidal type distortion , 1988 .

[15]  T. Rojo,et al.  Magnetostructural correlations in parallel square-planar halo-bridged copper(II) dimers. Part II: Structure and magnetic properties of [Cu2(terpy)2Br2](PF6)2 , 1987 .

[16]  C. Landee,et al.  Strong antiferromagnetic exchange in a bromide-bridged copper dimer, bis(.mu.-bromo)bis[bromobis(tetramethylene sulfoxide)copper(II)]. Structure, susceptibility, and magnetostructural correlations , 1986 .

[17]  R. Willett.  Magnetic Susceptibility of Paraquat Hexabromodicuprate(II): Comparison of the Magnetochemistry of Copper(II) Chloride and Copper(II) Bromide Salts. , 1986 .

[18]  K. Wieghardt,et al.  Ferromagnetic intramolecular interactions in a bis(.mu.-bromo)-bridged copper(II) dimeric compound: crystal structure and molecular structure determination, electron paramagnetic resonance studies, and magnetic susceptibility measurements on bis(.mu.-bromo)bis(diethylenetriamine)copper(II)] perchlor , 1985 .

[19]  M. Melnik.  Study of the relation between the structural data and magnetic interaction in oxo-bridged binuclear copper(II) compounds , 1982 .

[20]  D. Hodgson,et al.  Synthesis and structural and magnetic characterization of the dimeric complex bis[dibromobis(4-methyloxazole)copper(II)] , 1982 .

[21]  James W. Hall,et al.  Exchange Coupling in the Alternating Chain Compounds Catena-Di-micron-chlorobis(4-Methylpyridine)Copper(II), Catena-Di-micron-bromobis-(N-Methylimidazole)Copper(II), Catena-hexanedionebis(Thiosemicarbazato)Copper(II), and Catena-octanedionebis(thiosemicarbazato)Copper(II). , 1981 .

[22]  W. Hatfield.  New magnetic and structural results for uniformly spaced, alternatingly spaced, and ladder‐like copper (II) linear chain compounds (invited) , 1981 .

[23]  D. Hodgson,et al.  Relation between the singlet-triplet splitting and the copper-oxygen-copper bridge angle in hydroxo-bridged copper dimers , 1976 .

[24]  Roald Hoffmann,et al.  Orbital interactions in metal dimer complexes , 1975 .

[25]  B. C. Gerstein,et al.  Models and Magnetism in One‐Dimensional Systems; Low‐Temperature Magnetic Susceptibilities of Dimethylammonium Trichlorocupate (II) and Tetramethylammonium Trichloronickelate (II) , 1972 .