Multinuclear silver -ethynide supramolecular synthons for the construction of coordination networks

This thesis describes our effort to explore, develop and utilize the silver-ethynide interaction in new kinds of metal-ligand supramolecular synthons for the construction of silver(I) coordination networks.;The reaction of Li-C≡C-Ca≡C-Li (generated in situ from hexachloro-1,3-butadiene and nBuLi) with AgNO3 led to the generation of a new silver carbide, silver 1,3-butadiynediide (Ag2C4). A series of fifteen double and multiple salts of Ag2C4 were synthesized by dissolving this polymeric starting material Ag2C4 in a concentrated aqueous solution of soluble silver salts (e.g. AgNO3, AgCF 3CO2, AgC2F5CO2). The silver-ethynide interaction may be conceived as a new kind of supramolecular synthon for the construction of 1-D, 2-D and 3-D coordination polymers. The terminal silver-ethynide interactions that are assigned in diverse configurations can be conveniently classified into three types: sigma, pi and mixed (sigma,pi), and tuned by variation of ancillary anionic ligands. In addition, the controlled hydrolysis of hexafluorophosphate led to the generation of the second silver quadruple salt Ag2C4 · 4AgNO3 · AgPF 2O2 · Ag3PO4 (4). The (F)2(H2O)18 fluoride-water tape in Ag 2C4 · 2AgF · 10AgC2F5CO 2 · CH3CN · 12H2O (10) and the (C4)3 Ag18 aggregate in 3Ag 2C4 · 12AgC2F5CO2 · 5[BzMe3N)C2F5CO2] · 4H 2O (15) are both unprecedented among silver(I)complexes.;Systematic investigation on silver(I) tert-butylethynide complexes resulted in the establishment of the general utility of the silver-ethynide supramolecular synthon with an alkyl tail. Upon the addition of nitrile ligands from CH3CN, CH3CH2CN to (CH3) 3CCN, adjacent silver ethynide moieties tBu-C≡C⊃Ag 5 approach closer to each other, and the resulting crystal structure transforms from a 2-D hydrogen bonding network, through a 2-D network held by hydrogen bonding and coordination, to a 2-D coordination network. Employment of the multidentate dicarboxylate ligand O2CCF2CF 2CO2 and the dinitrile ligand NC(CH2)4CN led to the formation of higher-dimensional networks.;Synthetic and structural studies were carried out on a series of silver(I) complexes of phenylethynide and phenylethynide derivatives with alkyl substituents (methyl, tert- butyl, trifluoromethyl) at variable positions (p-, m-, o-) on the aromatic ring. The invariable appearance of the mu4- and mu5-ligation modes of the ethynide moiety in ten silver(I) complexes reaffirms the general utility of the silver-arylethynide supramolecular synthon Ar-C≡C⊃Agn( n = 4, 5) in coordination network assembly.;The ensuing study of silver(I) phenylenediethynide complexes led to the recognition of another kind of supramolecular synthon, Agn⊂ C2---R---C2⊃Agn (R= p-, m-, o-C6H4; n = 4, 5).;Incorporation of heteroaromatic rings (pyridyl, pyrazinyl, pyrimidyl and thienyl) in the silver-ethynide supramolecular synthon led to a series of silver(I) double salts of various heterocyclic ethynide ligands. Through variation of the relative orientations between the ethynide moiety and heteroatom as well as between heteroatoms, different coordination networks were generated.;The above-mentioned structural studies of silver-ethynide complexes of aromatic or heteroaromatic ligands indicate that pi-pi stacking plays a pivotal role in the self-assembly of corresponding silver-ethynide synthons. Investigation of the silver(I) complexes of phenylethynide and its derivatives with different substituents (methyl, tert- butyl) in variable positions (o-, m-, p-) on the aromatic ring shows the relative position and the bulk of substituents both affect the pi-pi stacking between adjacent phenyl rings. Furthermore, a comparative study of pi-pi stacking in the nitrate complexes Ag2(m-C≡CC 6H4C≡C)] · 5AgNO3 · 3H 2O (38), [(3-AgC≡C)-py] · 3AgNO3 (45), 2[(2-AgC≡C)-pyraz] · 6AgNO3 3H 2O (50) and 2[2,3-(AgC≡C)2-thienyl] · 10AgNO3 (56) suggests that the pi-electron deficiency of the aromatic ring also weakens this non-covalent interaction. (Abstract shortened by UMI.).