The novel complex{[Co(bipy)(azpy)_(2)(NCS)_(2)]·H_(2)O}n(where bipy=4,4′bipyridine,azpy=4,4′azobisp yridine)has been synthesized and characterized by elemental analyses,IR,UV,thermal analyses,and variable tempe...The novel complex{[Co(bipy)(azpy)_(2)(NCS)_(2)]·H_(2)O}n(where bipy=4,4′bipyridine,azpy=4,4′azobisp yridine)has been synthesized and characterized by elemental analyses,IR,UV,thermal analyses,and variable temperature magnetic susceptibility.The crystal(C_(32)H_(26)CoN_(12)OS_(2),Mr=717.70)belongs to the orthorhombic,space group Pnna,a=2.21312(16)nm,b=1.40403(10)nm,c=1.14237(8)nm,V=3.5497(4)nm^(3),Z=4,Dc=1.343g·cm^(-3),μ=0.645mm^(-1),F(000)=1476,and final R_(1)=0.0691,wR_(2)=0.1129 for 231 parameters and 1674 observed reflections[I>2.00σ(I)].The Co(Ⅱ)atom is,in a distorted octahedral geometry,coordinated by six nitrogen atoms from two bridging bipy,two monodentate azpy,and two thiocyanate groups.The bridging ligand bipy links Co(Ⅱ)atoms to form the infinite“rod"with terminal coordination azpy ligand acting as sidearms.Unprecedented three parallel interpenetrating two dimensional(4,4)networks and novel infinite triple helices are formed via hydrogen bonding interactions.CCDC:155588.展开更多
Three cobalt complexes bearing tunable,redox-active bipyridyl N-heterocyclic carbene(NHC)-based ligands have been studied for electrocatalytic hydrogen evolution from aqueous solutions.The effect of structural modific...Three cobalt complexes bearing tunable,redox-active bipyridyl N-heterocyclic carbene(NHC)-based ligands have been studied for electrocatalytic hydrogen evolution from aqueous solutions.The effect of structural modifications to the ligand framework is investigated across the catalyst series,which includes a non-macrocyclic derivative(1-Co)and 16-(2-Co)and 15-(3-Co)membered macrocycles.A structure-activity relationship is demonstrated,in which the macrocyclic complexes have greater activity compared to their non-macrocyclic counterpart with the most rigid catalyst,supported by the 15-membered macrocycle,performing best overall.Indeed,3-Co catalyzes H2 evolution from aqueous pH 4 acetate buffer with a Faradaic efficiency of 97%at a low overpotential of 330 mV.Mechanistic studies are consistent with formation of a cobalt-hydride species that is subsequently protonated to evolve H2 via a heterolytic pathway.展开更多
文摘The novel complex{[Co(bipy)(azpy)_(2)(NCS)_(2)]·H_(2)O}n(where bipy=4,4′bipyridine,azpy=4,4′azobisp yridine)has been synthesized and characterized by elemental analyses,IR,UV,thermal analyses,and variable temperature magnetic susceptibility.The crystal(C_(32)H_(26)CoN_(12)OS_(2),Mr=717.70)belongs to the orthorhombic,space group Pnna,a=2.21312(16)nm,b=1.40403(10)nm,c=1.14237(8)nm,V=3.5497(4)nm^(3),Z=4,Dc=1.343g·cm^(-3),μ=0.645mm^(-1),F(000)=1476,and final R_(1)=0.0691,wR_(2)=0.1129 for 231 parameters and 1674 observed reflections[I>2.00σ(I)].The Co(Ⅱ)atom is,in a distorted octahedral geometry,coordinated by six nitrogen atoms from two bridging bipy,two monodentate azpy,and two thiocyanate groups.The bridging ligand bipy links Co(Ⅱ)atoms to form the infinite“rod"with terminal coordination azpy ligand acting as sidearms.Unprecedented three parallel interpenetrating two dimensional(4,4)networks and novel infinite triple helices are formed via hydrogen bonding interactions.CCDC:155588.
文摘Three cobalt complexes bearing tunable,redox-active bipyridyl N-heterocyclic carbene(NHC)-based ligands have been studied for electrocatalytic hydrogen evolution from aqueous solutions.The effect of structural modifications to the ligand framework is investigated across the catalyst series,which includes a non-macrocyclic derivative(1-Co)and 16-(2-Co)and 15-(3-Co)membered macrocycles.A structure-activity relationship is demonstrated,in which the macrocyclic complexes have greater activity compared to their non-macrocyclic counterpart with the most rigid catalyst,supported by the 15-membered macrocycle,performing best overall.Indeed,3-Co catalyzes H2 evolution from aqueous pH 4 acetate buffer with a Faradaic efficiency of 97%at a low overpotential of 330 mV.Mechanistic studies are consistent with formation of a cobalt-hydride species that is subsequently protonated to evolve H2 via a heterolytic pathway.
