Structure and magnetism in a hydroxy bridged binuclear copper(II) system with a "tunable" binuclear centre

Abstract

The molecular structure of [Cu2(PAP)(OH)(IO3)3]•4H2O (PAP = 1,4-di(2′-pyridyl)aminophthalazine) has been determined by single crystal X-ray diffraction. [Cu2(PAP)(OH)(IO3)3]•4H2O belongs to the space group P21/c with a = 7.266(1), b = 15.269(1), c = 25.870(1) Å, β = 96.40(I)°, V = 2852.2 Å3, Z = 4. The copper coordination geometry lies between a square pyramid and a trigonal bipyramid and the two copper(II) centres are bridged by three groups: N2 (phthalazine), hydroxide, and bidentate iodate, in a structure which is analogous to that reported for [Cu2(PAP)(OH)Cl3]•1.5H2O. Replacing the chlorine bridge by iodate has the effect of forcing the two metal centres further apart, thus creating a larger Cu—O—Cu bridge angle. This increase in oxygen bridge angle (101° to 114°) is also reflected in the enhanced antiferromagnetic exchange (−2J(Cl) = 201 cm−1, −2J(IO3) = 335 cm−1). Other groups of varying size (e.g. Br, NO3, SO4) can act as bridges between the two copper centres in systems of this sort with the resultant variation in copper–copper separation and oxygen bridge angle.

catena-Poly{μ-(2,2'-bipyrimidine-N,N':N'',N''')-[(nitrato-O,O')copper(II)]-di-(μ-nitrato-μ-O)-[(nitrato-O,O')copper(II)]}, [Cu2(NO3)4(C8H6N4)]

“…Binuclear Cu ll complexes with ligands containing N atoms have been widely investigated in recent times since they are of great significance in biological systems (De Munno, Denti & Dapporto, 1983;Thompson, 1983;Dapporto, De Munno, Sega & Mealli, 1984). 2,2'-Bipyrimidine is a ligand with four N donor atoms whose Cu n and Fe I~ mixed complexes have been synthesized because they are possible models for cytochrome oxidase (Petty, Welch, Wilson, Bottomley & Kadish, 1980;McLendon & Smith, 1982).…”

Binuclear copper(II) complexes of the ligand 1,4-di(1′-methyl-2′-imidazolyl)phthalazine. Structure and magnetism of a hydroxyl bridged derivative

“…n adjacent molecule. The Cu---Cu separation (3.425 A) is much larger than those found in other monohydroxy bridged systems involving pyridyl aminophthalazine ligands, in which the substituent donor groups are separated from the diazine entity by an additional (nitrogen) atom (9,10,18). This has been attributed to the presence of five-membered chelate rings involving MIP as opposed to six-membered chelate rings in the other systems.…”

“…In an attempt to correlate the magnetic properties of a binuclear multibridged copper(I1) system with a single hydroxy bridge and such variables as oxygen bridge angle and metal-metal separation we have examined the structure and magnetism of a series of closely related binuclear copper(I1) compounds based on the phthalazine subunit as a binucleating building block (9,10). An approximately linear relationship is observed between the exchange integral and the oxygen bridge exchange much lower than expected based on its oxygen bridge angle.…”

The rotating ring-disk electrochemistry of the copper(II) complex of thyrotropin-releasing hormone

“…Hydroxo-bridges in Cu(II) complexes are not rare. There are many l-hydroxo-Cu(II) 2 examples [39][40][41][42][43] with one or two hydroxo-links. The geometry around the two Cu(II) centers is not always the same in each complex, but typically the Cu-Cu distance is 2.8-3.1 Å and the bond angle at the OH À is 95-105°.…”