RESUMO
The new conjugated organometallic polymer (-spacer-C[triple bond]C-Pt(PBu3)2-C[triple bond]C-)n (3; spacer = para-bis(diphenyl(tetramethyl)quinone diimine) and the cyclic mononuclear model complex, spacer'-C[triple bond]C-Pt(PEt3)2-C[triple bond]C x CuCl (4; spacer' = ortho-diphenyl-2,3,5,6-tetramethyl-1,4-benzoquinone diimine) were synthesized from the 1:1 condensation of the corresponding diethynyl ligands (2-para and 2-ortho (para- and ortho-diethynyl-diphenyl-2,3,5,6-tetramethylquinone diimine), respectively), with the trans-Pt(PBu3)2Cl2 for polymer 3 and cis-Pt(PEt3)2Cl2 for 4. The materials were characterized by GPC, DSC, ATG, and electrochemistry for polymer 3, and by X-ray diffraction for 4. Polymer 3 exhibits a M(n) of 18500, M(w) of 25000 with a PD of 1.37. The trans-geometry about Pt in polymer 3 was confirmed by 31P NMR and IR/Raman spectroscopy. The cyclic voltammogram study on the model complex trans-Pt(PBu3)2(C[triple bond]CPh)2, spacer 1-para (Me3Si-C[triple bond]C-R-C[triple bond]C-SiMe3; R = para-diphenyl-2,3,5,6-tetramethyl-1,4-benzoquinone diimine) and polymer 3 demonstrated that polymer 3 in the presence of trifluoroacetic acid (TFA) exhibits a quasi reversible 2-electron reduction process centered at 0.48 V versus SCE corresponding to the reduction of the protonated quinone diimine unit into the corresponding diamine. The UV-vis spectra of the spacer 2-para (440 nm) and polymer 3 (502 nm) are characterized by red-shifted charge transfer (CT) absorptions (C6H4C[triple bond]C --> quinone diimine for 2-para; and (C6H4C[triple bond]C)2Pt --> quinone diimine for polymer 3). These assignments are corroborated by density-functional theory (DFT) and time-dependent density-functional theory (TDDFT) computations. Polymer 3 is not luminescent in the solid state or in solution at 77 K and 298 K.
RESUMO
Two families of organometallic polymers built upon the bimetallic M2(dppm)2L(2)2+ fragments (M = Pd, Pt; dppm = bis(diphenylphosphino)methane, L = 1,4-diisocyano-2,3,5,6-tetramethylbenzene (diiso), 1,8-diisocyano-p-menthane (dmb), 1-isocyano-2,6-dimethylbenzene, 1-isocyano-4-isopropylbenzene, and tert-butylisocyanide) were synthesized and fully characterized (1H and 31P NMR, X-ray crystallography (model compounds), IR, Raman, chem. anal., TGA, DSC, powder XRD, 31P NMR T1 and NOE, light scattering, and conductivity measurements). Evidence for polymers in the solid state is provided from the swelling of the polymers upon dissolution and the formation of stand-alone films. However, these species become small oligomers when dissolved. The materials are luminescent in the solid state at 298 and 77 K and in PrCN solution at 77 K. These emissions result from triplet 3(d sigma d sigma*) states despite the presence of low-lying pi-pi* MO levels according to DFT calculations for the aryl isocyanide model compounds. The emission band maxima are located between 640 and 750 nm and exhibit lifetimes of 3-6 ns for the Pd species and 3-4 micros for the Pt analogues in PrCN solution at 77 K. No evidence of intramolecular excitonic photoprocesses was found in any of the polymers.
