Vibrational Spectroscopic Investigation of Rigid-Rod Platinum σ-Acetylide Polymers Containing Variable Acetylenic Microstructures

Abstract

A detailed study of the vibrational spectra of the rigid-rod Pt(II)−σ-acetylide polymers, [(PnBu3)2Pt−C⋮CC⋮CC⋮C−] n , [(PnBu3)2Pt−C⋮CC⋮C−] n , [(PnBu3)2Pt−C⋮CC6H4C⋮C−] n , [(PnBu3)2Pt−C⋮CC⋮CC6H4C⋮CC⋮C−] n , and [(AsnBu3)2Pt−C⋮CC6H4C⋮C−] n is reported. The backbone chain vibrations in these highly conjugated organometallic polymers can be analyzed by relating them to their centrosymmetric monomeric structures with an approximate C 2 h or D 2 h local symmetry. The extent of π-conjugation in the backbone can be monitored from the associated changes in the vibrational frequencies, in particular, the νC ⋮ C modes. In general, the vibrational spectra of the polymers suggest that the backbone is essentially alternating −C⋮C− in nature, without any contribution from allene-type structures (CC). The interruption of the acetylenic linkages with phenyl groups reduces the π-conjugation. The near-infrared FT-Raman spectra of the polymers show resonance enhancement of selected vibrations which occur along the direction of the polymer chain, presumably due to coupling with electronic transitions of the backbone. In addition, these polymers exhibit strong and substituent-sensitive fluorescence in their FT-Raman spectra.

Synthesis, Structure, and Reactivity of sp Carbon Chains with Bis(phosphine) Pentafluorophenylplatinum Endgroups: Butadiynediyl (C4) through Hexadecaoctaynediyl (C16) Bridges, and Beyond

“…Interestingly, PtC 12 Pt, Pt'C 12 Pt', and PtC 16 Pt exhibit one more absorption than predicted theoretically for H(CC) 6 H and H(CC) 8 H. [13] The vibrational spectra of polymers based upon the PtC x repeat unit [-Pt(PR 3 ) 2 (C C) n -] (n 2, 3) have also been analyzed in detail. [36] The 31 P NMR data in J PPt coupling constants, which can be more accurately determined, decrease with chain length in every series of compounds. In the case of PtC x Pt, plots versus 1/n are linear (r 0.99) [37] and predict a value of 2563 Hz for PtC I Pt.…”

Generation and Coupling of [Mn(dmpe)2(CCR)(CC)]. Radicals Producing Redox‐Active C4‐Bridged Rigid‐Rod Complexes

“…[50] Other relevant bands in these spectra are ñ(C 3 ) vibrations of the C 4 chain, [5] which appear at around ñ % 1040 cm…”

“…The symmetric d 5 trans-bisalkynyl complexes [Mn(dmpe) 2 (9). Complex 9 proved to be unstable with regard to ligand disproportionation reactions and could therefore not be oxidized to a unique Mn III product, which prevented its further use in acetylide coupling reactions.…”

Organometallic Polymers of the Transition Metals

“…In the early 1990s, there were a number of reports on the synthesis of rigid-rod metal-containing polyynes by Lewis and coworkers using bis(trimethylstannylacetylides). [295][296][297][298][299][300][301][302] High-molecularweight ruthenium-, iron-and osmium-based polyynes were Scheme 64.…”