Copper complexes of polyfunctional phthalazines. Mononuclear and polynuclear derivatives

Abstract

. Can. J. Chem. 60,2583Chem. 60, (1982. Mononuclear, binuclear, and trinuclear copper(I1) complexes of the tetradentate ligands 1,4-di(2'-pyridyl) aminophthalazine (PAP) and 1,4-di(4'-methyl-2'-pyridyl) aminophthalazine (PAP4Me) and binuclear complexes of the tetradentate ligand 1,4-di(6'-methyl-2'-pyridyl) aminophthalazine (PAP6Me) are reported. In a series of binuclear carboxylate derivatives carboxylate bridges exist between copper centres in all cases and in some cases oxygen bridges (hydroxide or methoxide) are indicated. In all other polynuclearderivatives hydroxide bridges are anticipated on the basis of analytical, spectral, and magnetic data. The ligandsexist as anionic groups in some binuclear carboxylate derivatives while in the other polynuclear systems neutral ligands are found. In reactions in aqueous solution protonated mononuclear derivatives are obtained for both PAP and PAP4Me in cases where solutions of the metal salts are inherently acidic, followed by polynuclear, neutral ligand complexes which form when the pH increases. On a prepare les complexes mono-, bi-et trinuclkaires du cuivre(I1) des ligands tetradentates di(pyridy1 2')-1,4 aminophtalazine (PAP) et di-(methyl-4' pyridyl-2')-1,4 aminophtalazine (PAP4Me) et les complexes binuclkaires du ligand tetradentate di(methy1-6' pyridyl-2')-1,4 aminophtalazine (PAP6Me). Dans une sCrie de derives carboxylates binucltaires, il existe dans tous les cas des ponts carboxylates entre les centres cuivre et, dans certains cas, on trouve des ponts oxygknes (hydroxyde ou methylate). En se basant sur des donnees analytiques, spectrales et magnetiques, on prkvoit qu'il existera des ponts hydroxydes dans tous les autres derivks polynucleaires. Les ligands existent sous forme de groupes anioniques dans certains carboxylates binucleaires tandis que, dans d'autres systkmes polynuclkaires, on trouve des ligands neutres. Lorsque les solutions de sels mCtalliques sont intrinsequement acides, on obtient des derives mononuclCaires protones avec le PAP et le PAP4Me en solution aqueuses e t des complexes polynucleaires de ligands neutres lorsque le pH augmente. On n'obtient pas de complexes mononucleaires protones avec le PAP6Me alors que des facteurs stCriques empechent la formation de tels derives. On a observe de faibles moments magnetiques ( 1.1-1.5 BM) pour la plupart des complexes ayant un pont hydroxyde tandis qu'on observe des valeurs plus faibles (< 0.70 BM) pour deux complexes binucleaires du PAP6Me; ceci indique qu'il existe une possibilitk d'un fort echange antiferromagnetique entre les centres mCtalliques. Une etude preliminaire du complexe [CU,(PAP~M~)(OH)(NO,)~(H~O)~]NO, par cristallographie de rayons X indique une structure binuclkaire triplement pontCe incluant un pont nitrate bidentate et un pont hydroxyde avec un angle du pont oxygkne de 115,2".[Traduit par le journal]

Mononuclear and binuclear copper(II) complexes of some polyfunctional pyridyl phthalazines

“…2) in which steric constraints imposed by the substituent methyl groups on the pyridine rings are likely to differ from those of the previously reported systems. Earlier studies indicate that the pK, of PAP is close to 3.8 and that the ligand can behave as a neutral, anionic, or cationic entity (10)(11)(12). In its neutral form T--T'~: charge transfer absorptions were found to occur in the range 27400-29600 cm-I, while for anionic systems the lowest energy charge transfer band was found to occur between 24000 and 25600 cm-' (10).…”

“…2) were prepared by the same methods used for the synthesis of other previously reported pyridylphthalazines ( 10,12). Further details on their syntheses and the general properties of these and other pyridylphthalazines will be published elsewhere.…”

“…2) have shown a preference for the formation of binuclear complexes in which two metals are bound to the same ligand in a multiple bridged structural arrangement (10)(11)(12)(13)(14)(15)(16)(17). Polynuclear derivatives involving three copper centres have also been reported ( 1 1 , 12) and in some cases protonated, mononuclear derivatives are found in which the formation of a protonated ligand is seen as the result of the sensitivity of these ligands to even mildly acidic conditions which are common in Can.…”

“…nitrogen donor groups in multibridged structures involving, in on Busycon canaliculatum oxyhemqcyanin have suggested a cases, h~d r o x~ bridges beb~een the metal centres copper-copper separation of 3.67 A in a proposed structure (10)(11)(12)(13). The ligands have included PAP(l,4-di(2'-pyridy1)-with three imidazoles bound to each copper centre, a peroxide aminophthalazine) and PAP4Me and PAP6Me which have bridge, and another endogenous protein ligand bridge (5).…”

“…X-ray structures have shown that the biMegathura crenulata and Helix pom!tia and found the two nuclear centre in a series of hydroxy bridged species can be copper atoms to be separated by 3.55 A in a proposed structure tuned by varying a third bridging group ( Fig. 1) (10,(12)(13)(14). involving two imidazoles per copper, a peroxide bridge and a 1" general, systems of this sort have low room temperature protein ligand bridge in an approximately square planar strucmagnetic moments$ signalling exchange-coupled copper tenture (6).…”