2,2 :6 ,2":6 ’,2” -Quaterpyridine structure

Quadrupole splitting constants, 37 129 Quantum mechanical methods, 38 424 Quantum mechanical predication, lattice energies and, 1 181-186 2,2 6, 2 6",2"-Quaterpyridine coordination compounds, 30 104-106 Structure, 30 70 Quenching center, 35 321 organometallics, 19 93-98 chemical, 19 98... 

Lehn, J. M., Sauvage, J. P., Simon, J., etal, Synthesis and metal-complexes of a conformationally restricted quaterpyridine -crystal-structure of its dimeric dinuclear Cu (I) complex, [Cu2(pqp)2]2+. Nouv. J. Chim. - New J. Chem. 1983, 7, 413-420. 

The planar quaterpyridine ligand (190) can coordinate in a somewhat strained square-planar arrangement with Cn, Co , Co , Ni , Cr , and Pd but with potentially tetrahedral metal centers such as Cu or Ag a subtle interplay of steric factors (metal and ligand) allows the formation of dinuclear dibridged helical structures (see Section 8). ... 

In an early study by Lehn et al., it was also demonstrated that quaterpyridine (36) forms a monomeric copper(I) species (that is not helical), whereas with cop-per(II) a dimeric species is obtained these complexes may be interconverted elec-trochemically. The above monomeric copper(I) complex was shown by X-ray diffraction to have a tetragonal pyramidal structure [four basal nitrogens and an axial oxygen (water)] in the solid state. This ligand also yields a dinuclear complex with ruthenium(II) of type [Ru2L2] . ... 

The bis(methylthio)-substituted quarterpyridine, 4, 4"-bis(methylthio)-2,2 6, 2" 6, 2" -quaterpyridine (44), yields a binuclear copper(I) complex, but a mononuclear species with copper(II). ° A spectroelectrochemical study indicated that a redox-induced transformation occurs between these two complex species. The X-ray structure of the 2 2 [copper(I) ligand] helical complex confirmed that each copper is tetrahedrally co-ordinated to four pyridyl nitrogens from two ligand strands, with a short Cu-Cu distance of 3.32 A being present. 

The interaction of the chiral quaterpyridine 75, bearing fused chiral groups in the 5,6- and 5", 6" -positions, with copper(I) has been investigated. The respective ligand isomers were demonstrated to form structurally characterised P or M dinuclear double helicates in approximately 99% diasteromeric excess upon coordination to the above ion. ... 

Fig. 8. Structure of dinuclear double helicate with quaterpyridine [Cu2(L7)2]+. (From Fig. 6 in Constable, E. C, Elder, S. M. Hannon, M. J. Martin, A. Raithby, P. R. Tocher, D. A. J. Chem. Soc., Dalton Trans. 1996, 2423.)...

Figure 14(c)." " Interestingly, while the hexadenate sex-ipyridine can form a double helicate with the Jahn-Teller distorted copper(II), quaterpyridine does not because the preference for a distorted octahedral geometry of the metal ion is inconsistent with the helix-forming requirements of the ligand. As a result, reduction of the mononuclear cop-per(n) quaterpyridine complex results in redox-reversible helicate formation. One-electron oxidation of the compound gives a mixed-valence Cu(I)-Cu(ll) helicate, which on further oxidation decomposes to give the mononuclear Cu(II) species (Scheme 2). The Cu(II)/Cu(I) redox interconversion in helicates with various podands has been extensively studied and different electrochemical behavior is observed according to the structural feamres such as denticity, rigidity, and steric hindrance of the helicand. In one case, the mixed-valence Cu(II)/Cu(I) helicate complex is stabilized by specific metal-metal interactions and can be isolated and structurally characterized by X-ray crystallography. ...

Cruskie, M.P., Zoltewicz, J.A., and Abboud, JLA. (1995a) Revised structure and convergent synthesis of nemertelline, the neurotoxic quaterpyridine isolated from the hoplonemertine sea worm. J. Org. Chem., 60, 7491-7495. 

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