title: A highly stable rhenium-cobalt system for photocatalytic H(2) production: unraveling the performance-limiting steps.
abstract: Increased long-term performance was found for photocatalytic H(2) production in a homogeneous combination of [Re(NCS)(CO)(3)bipy] (1; bipy = 2,2'-bipyridine), [Co(dmgH)(2)] (dmgH(2) = dimethylglyoxime), triethanolamine (TEOA), and [HTEOA][BF(4)] in N,N-dimethylformamide, achieving TON(Re) up to 6000 (H/Re). The system proceeded by reductive quenching of *1 by TEOA, followed by fast (k(1) = 1.3 x 10(8) M(-1) s(-1)) electron transfer to [Co(II)(dmgH)(2)] and subsequent protonation (K(2)) and elimination (k(3), second-order process in cobalt) of H(2). Observed quantum yields were up to approximately 90% (H produced per absorbed photon). The type of acid had a substantial effect on the long-term stability. A decomposition pathway involving cobalt is limiting the long-term performance. Time-resolved infrared (IR) spectroscopy confirmed that photooxidized TEOA generates a second reducing equivalent, which can be transferred to 1 (70%, k(2e)(-) = 3.3 x 10(8) M(-1) s(-1)) if no [Co(II)(dmgH)(2)] is present.
authors.affiliation: Institute of Inorganic Chemistry, University of Zürich, Switzerland.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Probst
authors.forename: Alexander
authors.initials: A
authors.lastname: Rodenberg
authors.forename: Miguel
authors.initials: M
authors.lastname: Guttentag
authors.forename: Peter
authors.initials: P
authors.lastname: Hamm
authors.forename: Roger
authors.initials: R
authors.lastname: Alberto