Photophysics of Tungsten and Molybdenum Arylcarbyne Complexes. Observation of the Lowest Excited State by Laser Flash Photolysis

Abstract

The photophysics of the series of tungsten and molybdenum arylcarbyne complexes Cp(CO){P(OMe)3}M⋮CAr (1a, M = W, Ar = phenyl; 1b, M = Mo, Ar = phenyl; 1c, M = W, Ar = o-tolyl; 1d, M = W, Ar = 2-naphthyl) has been examined by using absorption, emission, and transient absorption spectroscopy. Extended Hückel calculations indicate that the lowest excited state of these arylcarbyne complexes is based on a d(M) → π*(M⋮CAr) configuration. Consistent with this prediction, each of the complexes displays a weak, mid-visible absorption band which is attributed to the d → π* transition. The tungsten complexes 1a, 1c, and 1d also exhibit red luminescence with a lifetime in the 100−200 ns regime. Nanosecond laser flash photolysis studies indicate that the arylcarbyne complexes display a strong transient absorption with a maximum in the 400−450 nm region. Close correspondence between decay lifetimes obtained by luminescence and transient absorption indicate that the transient absorption may be assigned to the d → π* excited state.

Photophysics of tungsten–benzylidyne complexes derived from s-indacene: synthesis, characterization and DFT studies

“…For the monometallic complex 1 and homometallic complex 2, the value chemical shi of the carbonyl and alkylidyne groups appears at about 220 and 263 ppm respectively, these values are in agreement with the tungsten alkylidyne reported in literature. 37,38,60 The signal corresponding to the alkylidyne groups in the bond W^CPh is very weak, is not possible to see the satellites, and cannot be calculated the constant due the very low concentration of the species. The infrared spectra of compounds 1 and 2 show two intense carbonyl stretching bands at 1887 and 1978 cm À1 , consistent with local C 2v symmetry for the (CO) 2 W-unit.…”

“…Transition metal-alkylidynes, also known as metal-carbyne complexes [1][2][3][4] have been extensively studied over nearly four decades since their discovery. 5 Much of the interest in these compounds has been focused upon their diverse and fascinating reactivity, specially the catalytic metathesis of alkynes; [6][7][8][9][10][11][12][13][14] although many other aspects of their chemistry have also been explored, including the luminescence properties of their electronic states where the excited-state electron-transfer reactions of transition metal chromophores are integral to homogeneous systems for articial photosynthesis, dye-sensitized solar cells, and photoredox-based methods for organic synthesis, among other applications [15][16][17][18][19][20][21][22][23][24][25][26][27] and their utility as building blocks for electronic materials. [28][29][30][31][32][33][34][35][36] Regarding photophysical studies of the metal carbyne complexes of the half-sandwich type Cp(CO){P(OMe) 3 }M^C-R, where M ¼ Mo, W and R ¼ aryl, a reported was made by McElwee-White.…”

“…[28][29][30][31][32][33][34][35][36] Regarding photophysical studies of the metal carbyne complexes of the half-sandwich type Cp(CO){P(OMe) 3 }M^C-R, where M ¼ Mo, W and R ¼ aryl, a reported was made by McElwee-White. 37,38 These complexes display weak absorption bands in the visible region and long-lived luminescence. Theoretical and spectroscopic studies indicate that the low energy band is associated with the HOMO / LUMO transition, which is dominated by the d(M) / p*(M^C-Ar) conguration.…”

Electrocatalytic reductive dimerization of the 2,2′-bipyridyl tungsten alkylidyne complex [W(CC6H4NMe2-4)(NCMe)(CO)2{κ2-2,2′-(NC5H4)2}]+

“…The optoelectronic properties of Group 6 metal Fischer alkylidynes have been investigated to a limited extent with, for example, reports of photoluminescence in the TMEDA alkylidyne complex [W("CPh)Cl(CO) 2 {j 2 -Me 2 N(CH 2 ) 2 -NMe 2 }] (TMEDA = N,N,N 0 ,N 0 -tetramethylethylenediamine) and related cyclopentadienide derivatives [M(" CAr)(CO){P(OMe) 3 }(g 5 -C 5 H 5 )] (M = W, Mo; Ar = Ph, C 6 H 4 Me-2, C 10 H 7 -2) [1,2]. The photophysical properties of other d 0 -d 2 tungsten alkylidyne complexes have also been reviewed [3].…”

Bi- and poly(carbyne) functionalised polycyclic aromatics

“…Prior bis(alkylidynyl)arenes and polycyclic aromatic alkylidynes. 4,5,8,9 classical multi-step Fischer or Fischer-Mayr protocols. The disappointing yields obtained from these linear sequences, coupled with the thermal lability of the para-phenylene examples, most likely accounts for their lack of subsequent study.…”