Delocalization in Platinum−Alkynyl Systems:  A Metal-Bridged Organic Mixed-Valence Compound

Abstract

A complex featuring two triarylamine redox centers bridged by Pt, trans-bis(triethylphosphine)-bis{4-[bis(4-methoxyphenyl)amino]phenylethynyl} platinum(II), has been synthesized as a model system for pi-conjugated Pt-containing polymers. Analysis of the intervalence charge-transfer band displayed by its mixed-valence monocation affords a quantitative assessment of electronic delocalization through the Pt bridge; this is found to be only slightly smaller than that determined for a benzene-bridged analogue. These results are supported by density functional theory calculations, which show that the active orbitals involved in the electron-transfer process in both cases have similar delocalization through the bridging unit.

Computational and spectroscopic studies of organic mixed-valence compounds: where is the charge?

“…We find 5-7 to be localized (class II) in both solvents, in agreement with experimental observation. 5,7,8,10,[44][45][46][47][48][49][50][51][52] This is indicated by the ET barriers, the dipole moments, and the View Article Online asymmetry of the C Ar -N distances. As expected from the increasing donor capacity of the substituents on the central phenyl ring (H for 5, CH 3 for 6, and OCH 3 for 7), the amount of symmetry breaking tends to decrease from 5 to 7 in a given solvent (albeit 5 and 6 behave very similarly and only 7 is notably less localized).…”

“…This is confirmed by experimental observations (see below). 5,7,8,10,[44][45][46][47][48][49][50][51][52] Cation 8 exhibits the rather large central anthracene group and thus is a special case (see below). 8 Cations 5-7 move towards the border from the class II side.…”

“…29 For a test series of four MV bis-triarylamine radical cations we could show that a computational evaluation of ground-and excitedstate properties by this protocol allows a relatively fine bracketing of the localized/delocalized nature, the structure, and the spectroscopic parameters of such systems. In this contribution we will extend the validation of this protocol to a series of bistriarylamine radical cations with degenerate redox centers which have been well characterized experimentally 5,7,8,10,[44][45][46][47][48][49][50][51][52][53][54][55][56] and which shall serve as test cases to demonstrate how to apply DFT electronic structure calculations to discriminate between class II and class III MV systems. Furthermore we will apply the same computational protocol 29 to triarylamineperchlorotriphenylmethyl radical MV systems with nondegenerate redox centers.…”

Characterisation of a dipolar chromophore with third-harmonic generation applications in the near-IR

“…with the planes of the terminal aryl groups (Ar), consistent with the amine acting as a p-donor primarily to the bridging groups. However, it should be noted that, although all three angles in triarylamines are often comparable, both in simple compounds 46 and other triarylamine-based extended p-systems without strong p-acceptors, 47,48 they can show similar patterns of interplanar angles at the amine to that found in 1,…”

Charge Delocalization in a Homologous Series of α,α′-Bis(dianisylamino)-Substituted Thiophene Monocations

“…[36][37]50 Indeed, these absorptions fall into the spectral range in which intervalence absorptions of bis(triarylamine) radical cations are commonly observed. 16,20,[34][35][51][52][53][54][55][56][57][58][59][60][61] An important difference to the intervalence absorptions of coordination compounds 40,[62][63][64][65] are the comparatively large extinction coefficients of these bands, but this is a (favorable) peculiarity of organic mixed-valence compounds which has been noted many times before. Table 2.…”