Electronic Structure Optimization of PdZn-Graphitic Carbon Nitride Nanocomposites as Electrocatalysts for Selective CO2 to CO Conversion.

Herein, a novel PdZn/g-C3N4 nanocomposite electrocatalyst, PdZnGCN, prepared from a facile hydrothermal reduction procedure for an efficient CO2 to CO conversion has been examined. This composite catalyst reduces CO2 at a thermodynamic overpotential of 0.79 V versus RHE with a 93.6% CO Faradaic efficiency and a CO partial current density of 4.4 mA cm-2. Moreover, the turnover frequency for PdZnGCN reaches 20 974 h-1 with an average selectivity of 95.4% for CO after 1 h and an energy efficiency approaching 59%, which is superior to most reported noble metals and metal alloys as electrocatalysts. The enhanced catalytic activity of this nanocomposite is due to synergistic interactions between PdZn and g-C3N4 as evidenced by optimum work function, zeta potential, CO desorption rate, and downshifted d-band center. Furthermore, suppressed grain growth during the formation of nanocomposites also results in faster reaction kinetics, as demonstrated by a lower Tafel slope (93.6 mV/dec) and a larger electrochemically active surface, consequently enhancing the overall performance.

Conversion of Nitric Oxide into Nitrous Oxide as Triggered by the Polarization of Coordinated NO by Hydrogen Bonding.

Reduction of the {Co(NO)}(8) cobalt-nitrosyl N-confused porphyrin (NCP) [Co(CTPPMe)(NO)] (1) produced electron-rich {Co(NO)}(9) [Co(CTPPMe)(NO)][Co(Cp*)2 ] (2), which was necessary for NO-to-N2 O conversion. Complex 2 was NO-reduction-silent in neat THF, but was partially activated to a hydrogen-bonded species 2⋅⋅⋅MeOH in THF/MeOH (1:1, v/v). This species coupling with 2 transformed NO into N2 O, which was fragmented from an [N2 O2 ]-bridging intermediate. An intense IR peak at 1622 cm(-1) was ascribed to ν(NO) in an [N2 O2 ]-containing intermediate. Time-course ESI(-) mass spectra supported the presence of the dimeric [Co(NCP)]2 (N2 O2 ) intermediate. Five complete NO-to-N2 O conversion cycles were possible without significant decay in the amount of N2 O produced.

Ruthenium complexes of thiaporphyrin and dithiaporphyrin.

Successful synthesis and characterization of the six-coordinated complex [Ru(STTP)(CO)Cl] (1; STTP = 5,10,15,20-tetratolyl-21-thiaporphyrinato) allowed the development of the coordination chemistry of ruthenium-thiaporphyrin through dechlorination and metathesis reactions. Accordingly, [Ru(II)(STTP)(CO)X] (X = NO(3)(-) (2), NO(2)(-) (3), and N(3)(-) (4)) was synthesized and analyzed by single-crystal X-ray structural determination and NMR, UV-vis, and FT-IR spectroscopic methods. An independent reaction of STPPH and [Ru(COD)Cl(2)] led to [Ru(III)(STTP)Cl(2)] (5), which possessed a higher-valent Ru(III) center and exhibited good stability in the solution state. This stability allowed reversible redox processes in a cyclic voltammetric study. Reactions of [Ru(S(2)TTP)Cl(2)] (S(2)TTP = 5,10,15,20-tetratolyl-21,23-dithiaporphyrinato) with AgNO(3) and NaSePh, also via the metathesis strategy, resulted in novel dithiaporphyrin complexes [Ru(II)(S(2)TTP)(NO(3))(2)] (6) and [Ru(0)(S(2)TTP)(PhSeCH(2)SePh)(2)] (7), respectively. The structures of 6 and 7 were corroborated by X-ray crystallographic analyses. Complex 7 is an unprecedented ruthenium(0)-dithiaporphyrin with two bis(phenylseleno)methanes as axial ligands. A comparison of the analyses of the crude products from reactions of NaSePh and CH(2)Cl(2) with or without [Ru(S(2)TTP)Cl(2)], further supported by UV-vis spectral changes under stoichiometric reactions between [Ru(S(2)TTP)Cl(2)] and NaSePh, suggested a reaction sequence in the order of (1) formation of a putative [Ru(II)(S(2)TTP)(SePh)(2)] intermediate, followed by (2) the concerted formation of PhSe-CH(2)Cl and simultaneously a reduction of Ru(II) to Ru(0) and finally (3) nucleophilic substitution of PhSeCH(2)Cl by excess PhSe(-), resulting in PhSeCH(2)SePh, which readily coordinated to the Ru(0) and completed the formation of bis(phenylseleno)methane complex 7.

Facile nitrite reduction and conversion cycle of {Fe(NO)}(6/7) species: chemistry of iron N-confused porphyrin complexes via protonation/deprotonation.

Facile nitrite reduction was achieved using [Fe(II)(HCTPPH)NO] as the starting compound to react with NaNO(2). Stoichiometric studies allow the isolation of both {Fe(NO)}(6) and {Fe(NO)}(7) nitrosyl complexes and provide insight into the proton and electron transfer processes during the nitrite reduction. Treating [Fe(CTPP)NO] with acid or oxidizing [Fe(HCTPP)NO] with AgClO(4) yields intermediate [Fe(HCTPP)NO](+). The conversion cycles starting from {Fe(NO)}(6) [Fe(CTPP)NO] to {Fe(NO)}(6) [Fe(HCTPP)NO][ClO(4)] then to {Fe(NO)}(7) [Fe(HCTPP)NO] and vice versa were constructed.

Ag4L2 nanocage as a building unit toward the construction of silver metal strings.

Self-assembly of AgNO 3 with the semirigid tetratopic ligands 1,2,4,5-tetrakis(benzoimidazol-1-ylmethyl)benzene (TBim) and 1,2,4,5-tetrakis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene (TDMBim) afforded compounds [Ag 4(mu 4-TBim) 2(mu 2-eta (2)-NO 3) 2](NO 3) 2. (1)/ 2CH 2Cl 2.2CH 3OH ( 1mu (1)/ 2CH 2Cl 2.2CH 3OH) and [(NO 3 (-)) subset{Ag 4(mu 4-TDMBim) 2}][Ag(NO 3) 2](NO 3) 2.CH 2Cl 2.CH 3OH.4H 2O ( 2.CH 2Cl 2.CH 3OH.4H 2O), respectively. The structures of 1 and 2 were characterized by single-crystal X-ray diffraction analysis. Both compounds adopt a M 4L 2-type tetragonal metalloprismatic cage structure, [Ag 4(mu 4-L) 2] (4+), with strong intramolecular silver-silver contacts. Compound 1 is a discrete species, while compound 2 is a novel infinite chainlike supramolecular array involving silver metal strings assembled from a [Ag 4(mu 4-L) 2] (4+) nanocage and silver linkages. Thermogravimetric analyses of 1. (1)/ 2CH 2Cl 2.2CH 3OH and 2.CH 3OH.4H 2O indicate that the Ag 4L 2-cage structures of 1 and 2 both are thermally stable up to 330 degrees C. Results from an in situ (1)H NMR study of AgNO 3 and TDMBim in different molar ratios unambiguously revealed the successive self-organization process, in which self-organization of the molecular cage takes place initially followed by crystallization of the corresponding supramolecular arrays with silver metal strings.

Base controlled polydiazeniumdiolation of 4-heptanone and a new water layer structure.

In a stoichiometry-controlled reaction, nitric oxide adds to the enolate of 4-heptanone at ca. -23 degrees C to give mono-, bis-, or tris-diazeniumdiolate (-N2O2(-)) products: potassium 4-heptanone-3,3,5-tris(diazeniumdiolate) (1), potassium butanoate 2,2-bis(diazeniumdiolate) (2), and potassium butanoate 2-diazeniumdiolate (3). The diazeniumdiolate products are stable crystalline solids under ambient conditions and as solids exothermally decompose at high temperatures. Single-crystal X-ray data measured for the dihydrate 3 reveal a new layer aggregation, L4(4)8(8), as octameric water aggregates in a stair conformation which interacts minimally with the cation of the salt.

Formation of a sulfur-atom-inserted N-confused porphyrin iron nitrosyl complex by denitrosation and C-S bond cleavage of an S-nitrosothiol.

The reaction of nitrosothiol, Ph3CSNO, with a divalent iron N-confused porphyrin complex, Fe(HCTPPH)Br, yields a {Fe(NO)}6 iron nitrosyl complex with a sulfur atom inserted in the Fe-C bond. The crystal structure reveals a bent Fe-N-O geometry and an eta2-(C,S) bonding mode between iron and the C-S bond. A reaction mechanism involving a transnitrosation and a nitrosothiol C-S bond cleavage is proposed.

Rigidity-modulated conformation control: a strategy for incorporating flexible building motifs into metallacycles.

A rigidity-modulated strategy for the conformational control of a flexible motif in the self-assembly of metallacycles is described; the span of the rigid ligand directs the conformation of the flexible motif by fixing the M ... M separation, thereby dictating the structure of the metallacycles.

Molecular assembling using axial phenolate on an iron N-confused porphyrin complex.

The reaction of sodium phenolate and Fe(HCTPPH)Br assembles a dimeric iron(III) complex with a channel-like solid state packing; the intramolecular iron-to-iron distance of 8.864 A is the longest among the available N-confused porphyrin dimeric complexes.

Structural variations in novel silver(I) complexes with bitopic pyrazole/n-heterocyclic carbene ligands.

The synthesis and structural characterization of several new silver complexes of L (L = a bidendate ligand of pyrazole and N-heterocyclic carbene) are described. The result shows that the choice of counterions, N-substitutions of L, and reaction conditions are crucial which lead to a variety of structural motifs, including novel metallomacrocycles [Ag2(mu-L)2]2+ with or without Ag...Ag close contact, a mononuclear [AgL2]+ complex, and a [LAg(NO3)]n coordination polymer. In particular, the nonbonding Ag...Ag distance and the overall geometry of the metallomacrocycles are controllable with different N-substitutions and counterions. All these complexes have been determined by X-ray diffraction. The solid-state aggregates are retained in solution as supported by the electrospray mass spectroscopic studies.