Matrix photochemistry of the complexes (CO)5M  C(OMe)Ph (M  Cr, W) having close-lying reactive MLCT and LF states

Servaas, Peter C.; Stufkens, Derk J.; Oskam, A.

doi:10.1016/0022-328x(90)85082-a

Cited by 33 publications

(47 citation statements)

References 31 publications

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“…This observation is consistent with earlier studies which also observed an anti to syn isomerisation of alkoxycarbenes upon photolysis. 18,19 This confirms that the isomerisation is promoted following excitation into the lowest accessible excited state. The failure to observe any significant changes to the terminal ν CO bands following the photoinduced anti-to synisomerisation confirms that both isomers have identical (within experimental error) spectra in this region.…”

Section: Pure Ch 4 Matrix Studiessupporting

confidence: 63%

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An investigation into the photochemistry of, and the electrochemically induced CO-loss from, [(CO)₅MC(OMe)Me](M = Cr or W) using low-temperature matrix isolation, picosecond infrared spectroscopy, cyclic voltammetry, and time-dependent density functional theory

et al. 2015

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propanone singlet excited state was detected on the reaction path to the metallaketene species. This metallacyclopropanone excited state species has a lifetime of less than 100 ps and a characteristic bridging carbonyl band at 1770 cm −1 . The tungsten ketene species was also detected but in contrast to the chromium system, this forms directly from a low-lying triplet excited state. The electrochemical release of CO showed a greater efficiency for the chromium complex when compared to the tungsten.

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Section: Pure Ch 4 Matrix Studiessupporting

confidence: 63%

“…[17][18][19][20][21] Photoinduced anti to syn isomerisation of the carbene ligand and photoinduced CO-loss processes have been reported in these studies. However, no evidence for the formation of a metallacyclopropanone or metallaketene species was obtained.…”

Section: Introductionmentioning

confidence: 68%

An investigation into the photochemistry of, and the electrochemically induced CO-loss from, [(CO)₅MC(OMe)Me](M = Cr or W) using low-temperature matrix isolation, picosecond infrared spectroscopy, cyclic voltammetry, and time-dependent density functional theory

et al. 2015

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“…Experimental and theoretical calculations reported by Sierra et al support the proposal that this occurs through a MLCT triplet excited state. 7 Although a number of low temperature and time-resolved studies have investigated photo-induced CO release from chromium carbenes, [8][9][10] no previous data have been reported on the picosecond time scale or on using modern theoretical calculations to identify the nature of the excited state involved in CO release.The CO-releasing ability of [(CO) 5 CrC(C 4 H 8 N)CH 3 ] was determined both photochemically using 355 nm (LED) excitation and thermally (at 37 1C) using a myoglobin (Mb) assay. 2,11 Fig.…”

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confidence: 99%

Controlled CO release using photochemical, thermal and electrochemical approaches from the amino carbene complex [(CO)₅CrC(NC₄H₈)CH₃]

McMahon

Rochford

Halpin

et al. 2014

Phys. Chem. Chem. Phys.

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Multimodal photo, thermal and electrochemical approaches toward CO release from the amino carbene complex [(CO) 5 CrC(NC 4 H 8 )CH 3 ] is reported. Picosecond time resolved infrared spectroscopy was used to probe the photo-induced early state dynamics leading to CO release, and DFT calculations confirmed that CO release occurs from a singlet excited state.CO releasing molecules (CORMs) are an area of current interest due to the physiological role of CO in the body. 1,2 CO is endogenously generated during oxidative heme degradation by the heme oxygenase (HO) enzymes. 3 The potential therapeutic applications of CO include vasodilation, anti-inflammatory and anti-proliferative effects. CORMs have been developed to deliver CO in a controlled manner. However, there is a major challenge in controlled CO release, be it photochemically, thermally or enzymatically induced. It is well known that chromium carbene complexes can release CO both thermally and photochemically, as the resulting tetracarbonyl reactive intermediates have been used as synthons in organic chemistry. 4 Recently, Lynam et al. reported the suitability of heteroatom (amino, methoxy and thio) stabilised chromium carbenes as thermal CORMs. 5 Rapid CO release was observed for the thio-and methoxy carbenes (t 1/2 = 313 s and 306 s, respectively, for a 60 mM solution of the complex to achieve an Mb-CO concentration of 30 mM), compared to slow release in the case of the amino analogue which required more than 2 h for a 60 mM solution of the complex to form 10 mM of carboxy-myoglobin (Mb-CO). In addition the chromium carbonyls investigated, demonstrated the fastest and most regulated CO release characteristics compared to the molybdenum or tungsten complexes studied. 5 In this communication we set out to compare the rate of CO release from [(CO) 5 CrC(NC 4 H 8 )CH 3 ] using photochemical, thermal and electrochemical stimulation. To the best of our knowledge this is first example of a CORM involving electrochemical stimulation. In the present study we report our findings on a ps-time resolved infrared (ps-TRIR) study on [(CO) 5 CrC(NC 4 H 8 )CH 3 ] in conjunction with DFT calculations to investigate the excited state responsible for the CO release. Chromium Fischer carbenes have received significant attention as photochemical synthons for a range of organic compounds. Photolysis of [(CO) 5 CrC(XR)R 0 ] in the presence of imines, olefins, aldehydes, or alcohols are known to yield b-lactams, cyclobutanones, b-lactones or amino esters respectively. 6 The proposed mechanism for these reactions involves a metal-toligand charge transfer photoexcitation resulting in the formation of a ketene intermediate which is formed by the insertion of a cis-CO ligand into the adjacent Cr-carbene bond (Fig. 1). Experimental and theoretical calculations reported by Sierra et al. support the proposal that this occurs through a MLCT triplet excited state. 7 Although a number of low temperature and time-resolved studies have investigated photo-induced CO release from chromium carbene...

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“…In attempts to understand the photochemical reactions of Fischer carbene complexes, several matrix isolation and flash photolysis studies have been conducted using both Cr and W (but not Mo) complexes [5][6][7][8][9][10][11].Although the complexes studied and conditions used varied, several general conclusions were drawn:…”

Section: Introductionmentioning

confidence: 99%

“…2. Tungsten alkoxycarbene complexes underwent similar anti-syn rearrangements but were much less prone to undergo CO loss [5][6][7][8][9][10]. 3.…”

Section: Introductionmentioning

confidence: 99%

Photoinduced Reactions of Metal Carbenes in Organic Synthesis

Hegedus

2005

ChemInform

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Matrix photochemistry of the complexes (CO)5M  C(OMe)Ph (M  Cr, W) having close-lying reactive MLCT and LF states

Cited by 33 publications

References 31 publications

An investigation into the photochemistry of, and the electrochemically induced CO-loss from, [(CO)₅MC(OMe)Me](M = Cr or W) using low-temperature matrix isolation, picosecond infrared spectroscopy, cyclic voltammetry, and time-dependent density functional theory

An investigation into the photochemistry of, and the electrochemically induced CO-loss from, [(CO)₅MC(OMe)Me](M = Cr or W) using low-temperature matrix isolation, picosecond infrared spectroscopy, cyclic voltammetry, and time-dependent density functional theory

Controlled CO release using photochemical, thermal and electrochemical approaches from the amino carbene complex [(CO)₅CrC(NC₄H₈)CH₃]

Photoinduced Reactions of Metal Carbenes in Organic Synthesis

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Matrix photochemistry of the complexes (CO)5M  C(OMe)Ph (M  Cr, W) having close-lying reactive MLCT and LF states

Cited by 33 publications

References 31 publications

An investigation into the photochemistry of, and the electrochemically induced CO-loss from, [(CO)5MC(OMe)Me](M = Cr or W) using low-temperature matrix isolation, picosecond infrared spectroscopy, cyclic voltammetry, and time-dependent density functional theory

An investigation into the photochemistry of, and the electrochemically induced CO-loss from, [(CO)5MC(OMe)Me](M = Cr or W) using low-temperature matrix isolation, picosecond infrared spectroscopy, cyclic voltammetry, and time-dependent density functional theory

Controlled CO release using photochemical, thermal and electrochemical approaches from the amino carbene complex [(CO)5CrC(NC4H8)CH3]

Photoinduced Reactions of Metal Carbenes in Organic Synthesis

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An investigation into the photochemistry of, and the electrochemically induced CO-loss from, [(CO)₅MC(OMe)Me](M = Cr or W) using low-temperature matrix isolation, picosecond infrared spectroscopy, cyclic voltammetry, and time-dependent density functional theory

An investigation into the photochemistry of, and the electrochemically induced CO-loss from, [(CO)₅MC(OMe)Me](M = Cr or W) using low-temperature matrix isolation, picosecond infrared spectroscopy, cyclic voltammetry, and time-dependent density functional theory

Controlled CO release using photochemical, thermal and electrochemical approaches from the amino carbene complex [(CO)₅CrC(NC₄H₈)CH₃]