Structure−Optical Property Relationships in Organometallic Sydnones

Abstract

As part of an effort to develop a spectroscopic structure-property relationship in platinum acetylide oligomers, we have prepared a series of mesoionic bidentate Pt(PBu3)2L2 compounds containing sydnone groups. The ligand is the series o-Syd-(C6H4-C[triple bond]C)n-H, where n = 1-3, designated as Syd-PEn-H. The terminal oligomer unit consists of a sydnone group ortho to the acetylene carbon. We synthesized the platinum complex (Syd-PEn-Pt), the unmodified ligands (PEn-H), and the unmodified platinum complexes (PEn-Pt). The compounds were characterized by various methods, including X-ray diffraction, 13C NMR, ground-state absorption, fluorescence, phosphorescence, and laser flash photolysis. From solving the structure of Syd-PE1-Pt, we find the angle between the sydnone group and the phenyl group is 45 degrees . By comparison of the 13C NMR spectra of the sydnone-containing ligands, the sydnone complexes with the corresponding unmodified ligands and complexes not containing the sydnone group, the sydnone group is shown to polarize the nearest acetylenes and have a charge-transfer interaction with the platinum center. Ground-state absorption spectra of the complexes in various solvents give evidence that the Syd-PE1-Pt complex has an excited state less polar than the ground state, while the PE1-Pt complex has an excited state more polar than the ground state. In all the higher complexes the excited state is more polar than the ground state. The phosphorescence spectrum of the Syd-PE1-Pt complex has an intense vibronic progression distinctly different from the PE1-Pt complex. The sydnone effect is small in Syd-PE2-Pt and negligible in Syd-PE3-Pt. From absorption and emission spectra, we measured the singlet-state energy E(S), the triplet-state energy E(T), and the singlet-triplet splitting Delta E(ST). By comparison with energies obtained from the unmodified complexes, attachment of the sydnone lowers E(S) by approximately 0.1 eV and raises E(T) by approximately 0.1 eV. As a result, the sydnone group lowers Delta E(ST) by approximately 0.2 eV. The trends suggest one of the triplet-state singly occupied molecular orbitals (SOMOs) is localized on the sydnone group, while the other SOMO resides on the rest of the ligand.

Organometallic acetylides of PtII, AuI and HgII as new generation optical power limiting materials

“…62,63 The detailed photophysical investigations concerning this group of materials, especially for some Pt II acetylide compounds, indicate that they can be efficient triplet emitters even at room temperature (rt) and their main absorption bands can be moved down below 400 nm with only an extremely weak absorption band (absorption coefficient e o 2 dm 3 mol -1 cm -1 ) in the visible region. [64][65][66][67][68] The efficient triplet emission at rt together with good transparency features would render them promising OPL materials according to the RSA mechanism and some encouraging results have been obtained in the past few years. By a careful selection of the arylacetylide ligands, or by using different transition metal centers and tuning the molecular geometry, etc., organometallic acetylides, especially the Pt II acetylide compounds, become very effective materials in terms of their superior OPL/transparency trade-off optimization, even better than the RSA dyes such as C 60 , metalloporphyrins and metallophthalocyanines.…”

Stereochemical Effects on Platinum Acetylide Two-Photon Chromophores

“…The majority of the photophysical investigations reported to date have focused on linear platinum acetylide complexes in the trans configuration at the metal center. ,,,− This focus is partially due to the thermodynamic instability of the cis isomer with respect to the trans isomer in solution, specifically when the auxiliary ligands are monodentate phosphines such as PBu 3 and PEt 3 . However, platinum acetylides can be constrained into the cis configuration by the incorporation of chelating auxiliary groups such as bidentate phosphines (e.g., 1,2-bis­(diphenylphosphino)­ethane (dppe), 1,3-bis­(diphenylphosphino)­propane (dppp)), , diimine ligands such as 2,2′-bipyridine, , or more recently bidentate bis­(imidazolin-2-ylidenes) …”

Synthesis and Photophysical Properties of Laterally Asymmetric Digold(I) Alkynyls and Triazolyl: Ancillary Ligand and Organic Functionality Dictate Excited-State Dynamics

“…Polymetallynes have long been studied as photoactive materials. ,,,,− ,− The ease of modifying the alkynyl ligands, coupled with triplet-state photophysics in solution and the solid state, lends them to a variety of applications, including organic light emitting diodes (OLEDS), − optoelectronics, − sensors, ,, and nonlinear optics (NLO), − among others. , Much of this work has focused on polymeric and multinuclear Pt­(II) complexes. In these d 8 species, the heavy-metal atom facilitates intersystem crossing to the triplet excited state manifold.…”