53109-57-2Relevant academic research and scientific papers
Time-resolved IR study of the photobehavior of W(CO)5(4-acpy) (4-acpy = 4-acetylpyridine)
Johnson, Frank P. A.,George, Michael W.,Turner, James J.
, p. 4226 - 4229 (2008/10/08)
Fast time-resolved infrared spectroscopy (TRIR) is used to probe the photochemistry of W(CO)5(4-acetylpyridine) in n-heptane. Visible irradiation (510 nm) populates the lowest MLCT state, which is monitored by TRIR. Subsequent dissociation to W(CO)5?n-heptane, via equilibrium with the 3LF state, is also followed. On UV irradiation (308 nm), the LF state is populated directly and W(CO)5?n-heptane appears immediately. With 510-nm irradiation, the yield of W(CO)5?n-heptane as a function of temperature is measured to give a value for the energy gap between the lowest MLCT state and the 3LF state, ～4000 cm-1.
Time-resolved infrared spectrum of the MLCT excited state of W(CO)5(4-CNpyr) (4-CNpyr = 4-cyanopyridine): Photophysics and photochemistry
Glyn, Paul,Johnson, Frank P. A.,George, Michael W.,Lees, Alistair J.,Turner, James J.
, p. 3543 - 3546 (2008/10/08)
Fast time-resolved infrared spectroscopy is employed to probe the lower metal to 4-CNpyr charge-transfer (MLCT) excited state of W(CO)5(4-CNpyr) (4-CNpyr = 4-cyanopyridine). On visible irradiation, the CO stretching vibrations shift to higher frequency, confirming that in this excited state the metal center is oxidized. The excited state decays back to the ground state and, via the LF excited state, decomposes to W(CO)5 and 4-CNpyr. The rate constants for these processes are equal (ca. 4 × 106 s-1), suggesting that there is a rapid equilibrium between the MLCT and LF states.
Photochemistry of (alkene)pentacarbonyltungsten(0) complexes in rigid alkane at low temperature: Relative importance of dissociative loss of alkene and carbon monoxide
Pope, Keith R.,Wrighton, Mark S.
, p. 2792 - 2796 (2008/10/08)
UV irradiation (254 or 313 nm) of W(CO)5(alkene) (alkene = C2H4, C3H6, 1-C5H10) in methylcyclohexane at 77 K yields two primary photoprocesses, CO and alkene loss. The relative loss of alkene is approximately 2 times more important upon 313-nm irradiation than when irradiation is at 254 nm. Further, the relative importance of alkene loss increases approximately threefold: C2H4 3H6 5H10. The loss of alkene is accompanied by the formation of W(CO)5, while loss of CO gives the 16e W(CO)4(alkene) species. Since the spectrum of the CO-loss product from W(CO)5(C2H4) is nearly the same as that from W(CO)5(C3H6) or W(CO)5(1-C5H10), no evidence for W(CO)4(H)(π-allyl) complexes is found. Even W(CO)5(η2-1,4-pentadiene) and W(CO)5(η2-cyclopentadiene), having doubly allylic C-H bonds, do not yield a hydride upon light-induced loss of CO. The measurement of the quantitative ratio of alkene:CO loss has been made possible by a quantitative determination of the extinction coefficient, ε, for free CO at 2132 cm-1 in methylcyclohexane at 77 K. The values of εco were determined by measuring the absorptivity at 2132 cm-1 for known fractional light-induced conversion of Cr(CO)6, W(CO)6, and (η5-C5H5)W(CO)3CH3 to CO and the appropriate 16e metal carbonyl; the values of εco from these precursors are 420 ± 40, 390 ± 20, and 420 ± 20 M-1 cm-1, respectively. In a 2-methyltetrahydrofuran glass the value of εco is lower, 350 ± 20 M-1 cm-1.
