Dicopper Schiff base complex

A series of j8-diketonate Schiff base complexes (87 M = Ni, Cu, Pd, VO n=10, 12, 16) having a half disc-shape, was synthesised [164]. All the complexes, except the oxovanadium complexes, were mesomorphic (Colh), at relatively low temperatures. This approach was also applied to half-discshaped homodinuclear and heterodinuclear 1,3,5-triketonate Schiff base complexes, 88, and 1,3,5,7-tetraketonate Schiff base dicopper complexes, 89 [165]. The homodinuclear complexes 88, with M = M = Cu, X = OR, were mesomorphic showing Colh phases, whereas those with four chains (88 X = H) were not liquid-crystalline. Amongst the five heterodinuclear prepared (88 X = OR,n=14, Y = —CH2—CH2—, M = Cu, Pd, Ni, Mn, Co and M =Ni), only those with M = Cu, M = Ni and M = Pd, M =Ni, showed a mesophase, namely a Colh phase. A Colh phase was also observed for a structurally related compound, 89, (n=12, X = OR). 

Inspired by the results of aromatic-ring hydroxylation from the laboratory of Karlin and co-workers, a few groups provided further examples of such reactivity, including some structurally characterized complexes of modified m-xylyl-based pyridine-donor ligands (Schiff base and non-Schiff base acyclic ligands), as well as aliphatic amine donor ligands (179) (Cu-Cu 2.990 A),169 (180) (Cu-Cu 3.015 A),170 and (181) (Cu-Cu 2.999 A).171 172 A m-xylyl-based ligand system that was used by Mukherjee and co-workers in the formation of complex (181) also resulted in the isolation of a bis(/i-hydroxo)dicopper(II) complex (182) (Cu-Cu 3.004 A).171,172 Casella and co-workers demonstrated that when their dicopper(I) complex... 

A further extension of m-xylyl dicopper complexation and xylyl hydroxy la-tion is seen in a Schiff-base macrocycle [175], When dicopper(I) complex 38 is reacted with 02, one of the two arene rings is hydroxylated, again producing a phenoxo-bridged dicopper(II) species a peroxo-dicopper(II) intermediate is suggested as the actual oxidant. 

Figure 2. Experimental (A isomer) and computed (A isomer) low energy structures of the dicopper(I) complex of the macrocyclic Schiff-base ligand with para-xylylene spacer groups, and computed energy barrier (confirmed by NMR spectroscopy).125126...

Schiff base (206) reacts with copper(ii) to form bis-(heptane-2,4,6-trionato)-dicopper(ii) and (207). N-3-Hydroxy-n-propylsalicylaldimine forms two types of dimeric copper(ii) complexes. One type has copper atoms bridged by pairs of deprotonated alcoholic oxygen atoms of the ligand, the other type has... 

The reaction of the diprotonated cryptand (16) with Cu(CH3CN)4Bp4 in methanol gave a dinuclear copper(I) complex (18) of the neutral cryptand. The X-ray crystal structure of this complex (Fig. 12b) shows that both the integrity of the cryptand and the unusual trans-trans conformations of the dicarbimine functions found in the protonated ciwptand are retained in the structure of the complex. The Cu(I)...Cu(I) separation is 6.25A. This copper separation is well in excess of that reported, 3.04A, for the dicopper(I) complex, [L Cu2](C104)2, in which is the [3+2] Schiff base cryptand derived from 2,6-... 

Figure 2. Calculated structure of a dicopper/dipotassium complex of a multisite schiff base polytopic receptor molecule, containing the dibenzo-18-crown-6 moiety. Size of circles indicates atom types ranging from metal (largest) to oxygen, nitrogen, carbon, and hydrogen (smallest) respectively.

Figure 35 shows the molecular structure of the dicopper(I) complex Cu2L(SCN)2 of a 20-membered macrocyclic SchifF base ligand L which was prepared by the cyclic [2 -I- 2] condensation of two molecules of 2,5-... 

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