Mixed ligand polymers

The last series of examples of diisocyanide-containing polymers is the mixed-ligand polymers where two different bridging ligands are used to hold the polymer backbone. The polymers are of the general formula (Au—C = C—R—C=C—Au—C=N—R —N=C) where the list for R and R is given in Table 8.2.73,74... 

Figure 13, Seaming electron micrographs of a large particle of the mixed ligand polymer (left 1000 X, right 3000 )Q. (Reproduced with permission from reference 20. Copyright 2007 Elsevier.)...

The procedure described here is not limited to the preparation of polymers such as 2. Starting from the difunctional silane 3 we have synthesized a copolymer, poly(dimethyl-co-isocyanopropylmethyl-siloxane) > as well as a linear homopolymer, poly(isocyanopropyl-methylsiloxane) 8 (Scheme 2). Indeed, preparation of a monofunctional analogue of 2. and h creates the potential for end-capping with an isocyanide function any polymer containing other functional groups, thereby in principle permitting mixed ligand complexes of polymers to be accessed. 

Mohammad Jafar Soltanian Fard-Jahromi and Ali Morsali (2010) Sonochemical synthesis of nanoscale mixed-ligands lead(II) coordination polymers as precursors for preparation of Pb2(S04)0 and PbO nanoparticles thermal, structural and X-ray powder diffraction studies. Ultrason Sonochem 17(2) 435-440... 

When simple nickel(II) salts are treated with thiols, in most cases stable thiolate-bridged polymers are formed. In a number of cases, treating these polymers with either tertiary phosphines or isocyanides gave mononuclear mixed-ligand complexes (equation 204).1951 These mononuclear complexes, due to the presence of terminal thiolates which possess lone pairs, can further react with nickel(II) and give trinuclear complexes (equation 205).1952... 

FIGURE 14. The mixed-ligand coordination polymers (M = Cu, Ag). The conteranion is BF4... 

The electronic spectra for the new mixed-ligand ID polymers exhibit an absorption band at 272 nm, assigned to a MLCT (rather than ira arising from the phenyl group). Solid-state emission spectra were recorded for both the model compounds and the polymers. The luminescence appears as broad bands located between 480 and 550 nm. Large Stokes shifts were observed, and the corresponding emission lifetimes (t6) ranged between 18 and 48 i,s (Table 4). These experimental data indicate that these emissions are in fact phosphorescence. 

Polymer 139 is another example of a mixed-ligand 1-D polymer. The difference with 137 and 138 is that bromide ions replace the diisocyanides.124 The X-ray structure reveals two Ag-Br distances (2.7431(13) and 2.9453(14) A), and the dimension indicates ionic interactions. The structure also exhibits a staircase geometry as previously and the nonbonding Ag -Ag separations are 3.605(2) and 3.916(2) A for the dmpm- and Br-bridged fragments, respectively. Raman spectra exhibit v(Ag -Ag) of 48 cm-1, giving a weak approximate force constant of 0.03 mdyn A-1. 

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