Synthesis, structural characterisation and photophysics of anionic cyclometalated bis(alkynyl)(benzo[h]quinolinate)platinate(ii) species

Abstract

The alkynylation of [Pt(bzq)(µ-Cl)] 2 (bzqH = benzo[h]quinoline) with excess of LiC᎐ ᎐ ᎐ CR in diethyl ether leads to novel (7,8-benzoquinolinate)bis(alkynyl)platinate() monoanionic species [Pt(bzq)which have been isolated as tetrabutylammoniun salts. The molecular X-ray structures of 3 and 6 reveal the presence of discrete anions with bond lengths and angles similar to those of related cyclometalated Pt compounds and no evidence of π-π or Pt-Pt stacking interactions. The influence of the R substituent on the photophysics of the complexes has been examined by UV-visible absorption, emission spectroscopy and cyclic voltammetry. Complexes 1-6 show a similar strong luminescence in both the solid state (structureless emission) and frozen solutions (well-resolved vibronic structures) while the emissions in solution at room temperature are red shifted (relative to the glass) and weak. For these complexes, on the basis of TD-DFT calculations which reproduce the experimental structure of anion 3, [Pt(bzq)(C᎐ ᎐ ᎐ CPh) 2 ] Ϫ , the emissions are proposed to arise from mixed [π C᎐ ᎐ ᎐ CR/Pt d/π (bzq) π* bzq] transitions. In contrast, complex 7 which contains the extended p-phenylethynylphenylacetylide ligand, C᎐ ᎐ ᎐ CC 6 H 4 -C᎐ ᎐ ᎐ CPh, displays a structured emission both at 298 K and in glassy CH 2 Cl 2 solutions. In this case the lack of a significant rigidochromism and DFT theoretical calculations support the involvement of a low-lying, metal perturbed acetylenic 3 ππ* (C᎐ ᎐ ᎐ CC 6 H 4 -C᎐ ᎐ ᎐ CPh) excited state.

Homo‐ and Heteropolynuclear Platinum Complexes Stabilized by Dimethylpyrazolato and Alkynyl Bridging Ligands: Synthesis, Structures, and Luminescence

“…This fact concerning the structure, that is in line with the lower (C C) vibration observed in the IR spectra (ñ = 1948 in complex 4 as opposed to 2039 cm À1 in complex 3), clearly points to a stronger Au-h 2 (acetylenic) bonding interaction, contrasting with the relatively low number of reported complexes of type bis(h 2 -alkynyl)Au. [103] The PtÀC, [67][68][69][70][71][72][79][80][81] PtÀN, [52,53,[73][74][75][76][77][78] and MÀN bond lengths [37, 38, 43-50, 52, 54, 55, 64, 92, 105-111] are similar to those observed in related pyrazolate complexes.…”

“…The IR spectrum of complex 1 shows several absorptions around 3200 cm À1 due to the NÀH bonds and two ñA C H T U N G T R E N N U N G (CC) absorptions consistent with a cis configuration of the s-alkynyl ligands around the Pt II center. [67] The 1 H NMR spectrum shows, in addition to the aromatic Ph protons, two sets of signals due to the Hdmpz groups, indicating that they are inequivalent at room temperature, probably due to the hindered rotation around the Pt À N bonds. The structure of complex 1 as evaluated by X-ray diffraction analysis ( Figure 1, Table 1) confirms the cis arrangement of both phenylethynyl and Hdmpz groups.…”

“…The Pt(2)ÀN and central PtÀC s bond lengths are in the range of those found in related pyrazolate [52,53,[73][74][75][76][77][78] and m,h 2 -alkynyl platinum(ii) complexes, [67][68][69][70][71][72][79][80][81] and the structural details concerning the alkynyl fragments are common for m,h 2 -alkynyl ligands. [79][80][81] The side platinum atoms, Pt(1A) and Pt(3A), exhibit a distorted square-planar environment that is considered to be formed by the C and P donor atoms of the cyclometalated phosphine, the N atom of the bridging dmpz and the midpoint ((X(1A) for Pt(1A), X(1B) for Pt(3A)) of the pbonded C a C b vector; the angles between cis ligands deviate significantly from 908.…”

A Luminescent Heteronuclear Cluster Featuring an Unusual Cu6 Boat‐Shaped Core Assembled by Two Dialkynyl‐Cycloplatinated Units

“…The presence of different bonding modes in the alkynyl groups is reflected in its IR (Nujol) spectrum, which exhibits several [70] clearly support the hypothesis that the pyridyl groups are involved in the coordination.…”

“…In (NBu 4 )[Pt(bzq)(CϵC-C 5 H 4 N-2) 2 ] a similar band is observed at 393 nm. [70] The coordination of the CϵC-C 5 H 4 N-2 to copper centers, which decreases the donor capabilities of the acetylide groups towards the Pt center could explain the observed shift to higher energies (393-374 nm). The cluster also exhibits a weak low-energy band at 425 nm (ε = 1.2 ϫ 10 3  -1 cm -1 ), which obey Beers' Law in the concentration range studied (10 -4 -10 -5 ), being tentatively attributed to the [Pt 2 Cu 6 (CϵC-C 5 H 4 N-2) 6 I 2 ] core.…”