PMID- 24692261
OWN - NLM
STAT- PubMed-not-MEDLINE
DCOM- 20150422
LR  - 20140508
IS  - 1521-3765 (Electronic)
IS  - 0947-6539 (Linking)
VI  - 20
IP  - 20
DP  - 2014 May 12
TI  - Photo- and electrocatalytic H2 production by new first-row transition-metal 
      complexes based on an aminopyridine pentadentate ligand.
PG  - 6171-83
LID - 10.1002/chem.201303317 [doi]
AB  - The synthesis and characterisation of the pentadentate ligand 
      1,4-di(picolyl)-7-(p-toluenesulfonyl)-1,4,7-triazacyclononane (Py2(Ts)tacn) and 
      their metal complexes of general formula [M(CF3SO3)(Py2(Ts)tacn)][CF3SO3], (M = 
      Fe (1Fe), Co (1Co) and Ni (1Ni)) are reported. Complex 1Co presents excellent H2 
      photoproduction catalytic activity when using [Ir(ppy)2(bpy)]PF6 (PSIr) as 
      photosensitiser (PS) and Et3N as electron donor, but 1Ni and 1Fe result in a low 
      activity and a complete lack of it, respectively. On the other hand, all three 
      complexes have excellent electrocatalytic proton reduction activity in 
      acetonitrile, when using trifluoroacetic acid (TFA) as a proton source with 
      moderate overpotentials for 1Co (0.59 V vs. SCE) and 1Ni (0.56 V vs. SCE) and 
      higher for 1Fe (0.87 V vs. SCE). Under conditions of CH3CN/H2O/Et3N (3:7:0.2), 
      1Co (5 muM), with PSIr (100 muM) and irradiating at 447 nm gives a turnover number 
      (TON) of 690 (n H2/n1Co) and initial turnover frequency (TOF) (TONxt(-1)) of 
      703 h(-1) for H2 production. It should be noted that 1Co retains 25 % of the 
      catalytic activity for photoproduction of H2 in the presence of O2. The 
      inexistence of a lag time for H2 evolution and the absence of nanoparticles 
      during the first 30 min of the reaction suggest that the main catalytic activity 
      observed is derived from a molecular system. Kinetic studies show that the 
      reaction is -0.7 order in catalyst, and time-dependent diffraction light 
      scattering (DLS) experiments indicate formation of metal aggregates and then 
      nanoparticles, leading to catalyst deactivation. By a combination of experimental 
      and computational studies we found that the lack of activity in photochemical 
      water reduction by 1Fe can be attributed to the 1Fe (II/I) redox couple, which is 
      significantly lower than the PSIr (III/II) , while for 1Ni the pKa value (-0.4) 
      is too small in comparison with the pH (11.9) imposed by the use of Et3N as 
      electron donor.
CI  - (c) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
FAU - Call, Arnau
AU  - Call A
AD  - Institut de Quimica Computacional i Catalisi (IQCC) and Departament de Quimica, 
      Universitat de Girona Campus Montilivi, 17071, Girona (Spain), Fax: 
      (+34) 972418150.
FAU - Codola, Zoel
AU  - Codola Z
FAU - Acuna-Pares, Ferran
AU  - Acuna-Pares F
FAU - Lloret-Fillol, Julio
AU  - Lloret-Fillol J
LA  - eng
PT  - Journal Article
DEP - 20140401
PL  - Germany
TA  - Chemistry
JT  - Chemistry (Weinheim an der Bergstrasse, Germany)
JID - 9513783
OTO - NOTNLM
OT  - cobalt
OT  - electrochemistry
OT  - homogeneous catalysis
OT  - hydrogen
OT  - photochemistry
OT  - water reduction
EDAT- 2014/04/03 06:00
MHDA- 2014/04/03 06:01
CRDT- 2014/04/03 06:00
PHST- 2013/08/23 00:00 [received]
PHST- 2014/01/16 00:00 [revised]
PHST- 2014/04/03 06:00 [entrez]
PHST- 2014/04/03 06:00 [pubmed]
PHST- 2014/04/03 06:01 [medline]
AID - 10.1002/chem.201303317 [doi]
PST - ppublish
SO  - Chemistry. 2014 May 12;20(20):6171-83. doi: 10.1002/chem.201303317. Epub 2014 Apr 
      1.