Structural and Spectroscopic Studies on Pt···Pt and π−π Interactions in Luminescent Multinuclear Cyclometalated Platinum(II) Homologues Tethered by Oligophosphine Auxiliaries

Abstract

The synthesis and structural, spectroscopic, and electrochemical properties of a series of trinuclear tridentate cyclometalated platinum(II) complexes tethered by bis(diphenylphosphinomethyl)phenylphosphine (dpmp) have been studied and compared with their mono- and binuclear homologues and a propeller-like congener. The X-ray crystal structures of several derivatives show the presence of a variety of intramolecular Pt.Pt, pi-pi, and C-H...O(crown ether) and intermolecular pi-pi interactions. The trinuclear complexes display strong absorption in the 400-600 nm region and show intense red to near-infrared phosphorescence with microsecond lifetimes in fluid and glassy solutions and in the solid state. These emissions are generally assigned as (3)MMLCT [dsigma-->pi(CNN)] in nature. The close similarities between the emission energies in acetonitrile solution and in the solid state at 298 K indicate that comparable Pt.Pt and pi-pi configurations are maintained in both media, and hence a relationship between the photophysical behavior of these lumophores and their solid-state structural features is proposed. The tendencies of the absorption and emission energies to red-shift from mono- to linearly tethered bi- and trinuclear Pt(II) species are evident. A light-emitting electrochemical cell using a trinuclear Pt(II) derivative as emitter has been demonstrated.

Ligand‐to‐Ligand Charge‐Transfer Transitions of Platinum(II) Complexes with Arylacetylide Ligands with Different Chain Lengths: Spectroscopic Characterization, Effect of Molecular Conformations, and Density Functional Theory Calculations

“…Similar to previous work on cyclometalated Pt II complexes containing acetylide ligands, [17] modification of the terpyridine ligand with electron-withdrawing groups also leads to a redshift in the lowest absorption energy band.…”

“…Consistent with the UV/Vis absorption spectral data of 5 and 6 (R = C 6 F 5 and Py, respectively), in which their absorption maxima, l 1 , are at higher energies than that of 7 a (R = Ph), the emission maxima of the former two complexes (l max = 524 and 545 nm for 5 and 6, respectively) show a blueshift from that of the latter (l max = 587 nm). In the cases of electron-donating substituents, R = C 6 H 4 -OCH 3 -4 (11), amine-substituted aryl groups (12,13,16,17,19, 21 a, and 22), fluorene-substituted aryl groups (20 a), these aryl-acetylide-platinum(II) complexes are nonemissive (f em < 0.01) in degassed CH 2 Cl 2 at ambient temperature. This phenomenon has similarly been reported in other terpyridine-Pt II complexes with nonsubstituted tpy ligands bearing electron-donating aryl-acetylide ligands.…”

Luminescent Platinum Complexes Having Sensing Functionalities

“…Luminescent trinuclear platinum(II) complexes have also been reported. 27 Besides platinum(II) complexes, much attention has been given to assembled systems involving gold(I) and copper(I) complexes. 28 Especially, trimer complexes with a triangular framework, such as [Au(CH 3 N=COCH 3 )] 3 (13) (Chart 5), are reported to exhibit interesting luminescence behavior such as vapochromism, solvatochromism, and solventstimulated photoemission.…”

(μ-Diphenylphosphanido-κ2 P:P′)bis[2,2′-(pyridine-2,6-diyl)diphenyl-κ3 C 1,N,C 1′)gold(III)] perchlorate acetonitrile solvate

“…For related literature, see: Goshe et al (2003); Kui et al (2006); Li et al (2006); Lu et al (2004); Wong et al (1998); Yam et al (2002).…”

“…Each Au atom is surrounded by one P atom from diphenylphosphanide ligand and two C atoms, one N atom from dpp in a square-planar geometry, the least-squares plane through Au III and dpp has a mean deviation of 0.04 (3) Å. The intramolecular Au···Au contact of 3.788Å is beyond a normal range of metal-metal interactions for d 8 metal ions (3.09-3.50 Å) (Yam et al, 2002;Goshe et al, 2003;Lu et al, 2004 (Li et al, 2006). The interplanar separation between two neighbouring dpp molecules are 3.40 and 3.57Å (Fig.…”