Efficient and selective electron mediation of cobalt complexes with cyclam and related macrocycles in the p-terphenyl-catalyzed photoreduction of CO[sub 2]

Journal Article · Wed Jan 27 00:00:00 EST 1993 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00055a032· OSTI ID:6566551

Matsuoka, Shinjiro; Yamamoto, Kiichi; Ogata, Tomoyuki; Kusaba, Mitsuhiro; Nakashima, Nobuaki; Yanagida, Shozo ^[1]; Fujita, Etsuko ^[2]

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1. Osaka Univ. (Japan)
2. Brookhaven National Lab., Upton, NY (United States)

Cobalt(III) complexes of cyclam (cyclam (L[sub 1]) = 1,4,8,11-tetraazacyclotetradecane) (Co[sup III]L[sub 1]) or related 14-membered tetraazamacrocycles (L[sub 2]-L[sub 8]) mediate electron transfer in the photoreduction of CO[sub 2] with p-terphenyl (OPP-3) as a photocatalyst and tertiary amines as sacrificial electron donors in methanolic acetonitrile. Tertiary amines (e.g., triethylamine (TEA)) used as electron donors play an important role in the electron mediation of Co[sup III]L[sub 1] through coordination, and the mediation of the amine-coordinated Co[sup III]L[sub 1] suppresses the degradative and competitive photo-Birch reduction of OPP-3 and enhances the activity of OPP-3, leading to efficient and selective formation of both carbon monoxide (CO) and formate (HCO[sub 2][sup [minus]]) without producing much H[sub 2]. The degradation of OPP-3 is mostly suppressed in the presence of [beta]-hydroxylated tertiary amines such as triethanolamine (TEOA) and tri-2-propanolamine (TIPOA), leading to much more efficient and selective production of CO and HCO[sub 2][sup [minus]]. As for the mechanism for the formation of HCO[sub 2][sup [minus]], the insertion of CO[sub 2] into intermediary hydride complexes such as [Co[sup III]L[sub 1](H[sup [minus]])(TEA)][sup 2+] derived from [Co[sup I]L[sub 1]][sup +] and H[sup +] is proposed. The structural and electrochemical properties of cobalt complexes of the 14-membered tetraazamacrocycles investigated (L[sub 2]-L[sub 8]) are also discussed in view of the distribution of the reduction products of CO, HCO[sub 2][sup [minus]], and H[sub 2]. 45 refs., 14 figs., 3 tabs.

• DOE Contract Number: AC02-76CH00016
• OSTI ID: 6566551
• Journal Information: Journal of the American Chemical Society; (United States), Vol. 115:2; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CARBON DIOXIDE
REDUCTION
CARBON MONOXIDE
SYNTHESIS
COBALT COMPLEXES
ELECTRON TRANSFER
ACETONITRILE
AMINES
CATALYSTS
PHOTOCHEMICAL REACTIONS
QUENCHING
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
COMPLEXES
NITRILES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
TRANSITION ELEMENT COMPLEXES
400500* - Photochemistry