Exploring ligand-centered electrocatalytic HO reduction: hydrogen generation with a soluble Ni(II) octabutoxyphthalocyanine complex.

A nickel(II) octabutoxyphthalocyanine complex demonstrating ligand-centered redox activity and pH dependence is reported and investigated as an electrocatalyst for hydrogen evolution from water. Spectro- and electrochemical methods were implemented to further elucidate the nature of the pH dependence and catalytic mechanism.

A comparison increasing the photodegradation power of a Ag/g-CN /CoNi-LDH nanocomposite: Photocatalytic activity toward water treatment.

For environmental applications, it is crucial to rationally design and synthesize photocatalysts with positive exciton splitting and interfacial charge transfer. Here, a novel Ag-bridged dual Z-scheme Ag/g-CN/CoNi-LDH plasmonic heterojunction was successfully synthesized using a simple method, with the goal of overcoming the common drawbacks of traditional photocatalysts such as weak photoresponsivity, rapid combination of photo-generated carriers, and unstable structure. These materials were characterized by XRD, FT-IR, SEM, TEM UV-Vis/DRS, and XPS to verify the structure and stability of the heterostructure.

Electrocatalytic Reduction of CO and HO with Zn(II) Complexes Through Metal-Ligand Cooperation.

Air and water-stable zinc (II) complexes of neutral pincer bis(diphenylphosphino)-2,6-di(amino)pyridine ("PNP") ligands are reported. These compounds, [Zn(κ-2,6-{PhPNR}(NCH))Br] (R=Me, 1; R=H, 2), were shown to be capable of electrocatalytic reduction of CO at -2.3 V vs.

Elucidating Two Distinct Pathways for Electrocatalytic Hydrogen Production Using Co Pincer Complexes.

Hydrogen gas is a sustainable energy source with water as the sole combustion product. As a result, efforts to catalyze H production are pertinent and widespread. The electrocatalytic H generating capabilities of two Co complexes, [Co(κ -2,6-{Ph PNR} (NC H ))Br ] with R=H (I) or R=Me (II), were presented for a variety of proton sources including trifluoroacetic acid (TFA), acetic acid (AA), and trifluoroethanol (TFE).

Electrocatalytic reduction of CO to CO and HCO with Zn(II) complexes displaying cooperative ligand reduction.

Air-stable zinc(II) pyridyl phosphine complexes, [Zn(κ-2,6-{PhPNMe}(NCH))Br] (1) and [Zn(κ-2-{PhPNMe}(NCH))Br] (2) are reported and 1 was capable of electrocatalytic reduction of CO at -2.3 V Fc to yield CO/HCOH in mixed water/acetonitrile solutions. DFT computations support a proposed mechanism involving electron transfer reactions from a species with the anionic PNP ligand ("L/Zn(II)").

Electrocatalytic H Generation from Water Relying on Cooperative Ligand Electron Transfer in "PN P" Pincer-Supported Ni Complexes.

Water is the most sustainable source for H production, and the efficient electrocatalytic production of H from mixed water/acetonitrile solutions by using two new air-stable nickel(II) pincer complexes, [Ni(κ -2,6-{Ph PNR} (NC H )Br ] (R=H I, Me II) is reported. Hydrogen generation from H O/CH CN solutions is initiated at -2 V against Fc , and bulk electrocatalysis studies showed that the catalyst functions with an excellent Faradaic efficiency and a turnover frequency of 160 s . A DFT computational investigation of the reduction behavior of I and II revealed a correlation of H formation with charge donation from electrons originating in a reduced ligand-localized orbital.

An integrated Re(i) photocatalyst/sensitizer that activates the formation of formic acid from reduction of CO.

The complex cis-[Re(bpy)(CO)]OTf (1OTf) is an integrated photosensitizer/catalyst for the selective visible light promoted photocatalytic reduction of CO. The formation of formic acid is unique among this class of Re catalysts, which yield CO as the selective product. A supplemental photosensitizer, Ru(bpy), considerably enhanced the performance of this catalyst.

Visible-Light Photocatalytic Reduction of CO to Formic Acid with a Ru Catalyst Supported by N,N'-Bis(diphenylphosphino)-2,6-diaminopyridine Ligands.

Visible-light photocatalytic CO reduction is carried out by using a Ru complex supported by N,N'-bis(diphenylphosphino)-2,6-diaminopyridine ("PNP") ligands, an unprecedented molecular architecture for this reaction that breaks the longstanding domination of α-diimine ligands. These competent catalysts transform CO into formic acid with high selectivity and turnover number. A proposed mechanism, with combined electron transfer and catalytic cycles, models the experimental rate of formic acid production.

Photocatalytic CO Reduction with Manganese Complexes Bearing a κ-PN Ligand: Breaking the α-Diimine Hold on Group 7 Catalysts and Switching Selectivity.

The fundamental challenge of reducing CO into more valuable energy-containing compounds depends on revealing new catalysts for this process. By removal of the long-standing limitation of α-diimine ligation, which is dominant in photocatalytic complexes in this area, new visible-light, CO-reducing photocatalysts based on Mn and Re supported by κ-PN phosphinoaminopyridine ligands were identified. These catalysts, [M{κ-(PhP)NH(NCH)}(CO)Br], displayed excellent product selectivity and, by a change of only the metal center, gave a dramatic product switch from CO with M = Mn to HCOH with M = Re.

Distinct Palladium(II) Carbene Complexes Supported by Six-Membered 1,3-Disubstituted Permidin-2-ylidene, Six-Membered N-Heterocyclic Carbenes.

The first synthesis, isolation, and characterization of permidin-2-ylidene complexes of Pd(II) is reported with entry resulting from either a direct reaction with isolable six-membered N-heterocyclic carbene or from the enetetramine, arising from dimerization of the carbene. Furthermore, a simplified method to prepare N,N'-disubstituted perimidinium bromide salts, precursors to 1,3-disubstituted perimidin-2-ylidene, was achieved using ammonium bromide as a source of weak acid. Through synthesis and nuclear magnetic resonance spectroscopic analysis of a carbene-phosphinidine adduct, an interrogation of the fundamental π-bonding ability of 1,3-diisopropylperimidin-2-ylidene revealed this interaction to be weak and of a similar order to unsaturated imidazol-2-ylidenes.

Electro- and Photocatalytic Generation of H Using a Distinctive Co "PN P" Pincer Supported Complex with Water or Saturated Saline as a Hydrogen Source.

Efficient electrocatalytic production of H from mixed water/acetonitrile solutions was achieved using three new Co complexes supported by the neutral pincer ligand bis(diphenylphosphino)-2,6-di(methylamino)pyridine ("PN P"). At -1.9 V vs.

Electrocatalytic generation of H from neutral water in acetonitrile using manganese polypyridyl complexes with ligand assistance.

A Mn(i) tris(2-pyridylmethyl)amine complex fac-[Mn(κ-tpa) (CO)]OTf carries out electrocatalytic hydrogen evolution from neutral water in acetonitrile. Bulk electrocatalytic studies showed that the catalyst functions with a moderate Faradaic efficiency and turn over frequency. DFT computations support the role of the tpa ligand as a shuttle to transfer of protons to the metal center.

Structural and electronic trends for five coordinate 1(st) row transition metal complexes: Mn(ii) to Zn(ii) captured in a bis(iminopyridine) framework.

The preparation and characterization of a series of divalent 3d transition metal complexes supported by a tridentate planar bis(iminopyridine) ligand are reported. The complexes {2,6-[PhC[double bond, length as m-dash]N(tBu2C6H3)]2C5H3N}MBr2 (M = Mn, Fe, Co, Ni, Cu, Zn), 1-6, were characterized by single crystal X-ray structural studies revealing complexes with pentacoordinate distorted square pyramidal coordination environments. This assembly of complexes provided a unique array for examining the relationship between experimental structure and computed electronic structure.

New Experimental Insight into the Nature of Metal-Metal Bonds in Digallium Compounds: J Coupling between Quadrupolar Nuclei.

Multiple bonding between atoms is of ongoing fundamental and applied interest. Here, we report a multinuclear ((1) H, (13) C, and (71) Ga) solid-state magnetic resonance spectroscopic study of digallium compounds which have been proposed, albeit somewhat controversially, to contain single, double, and triple Ga-Ga bonds. Of particular relevance to the nature of these bonds, we have carried out two-dimensional (71) Ga J/D-resolved NMR experiments which provide a direct measurement of J((71) Ga,(71) Ga) spin-spin coupling constants across the gallium-gallium bonds.

Electrocatalytic reduction of CO2 using Mn complexes with unconventional coordination environments.

New complexes, Mn{κ(3)-[2,6-{Ph2PNMe}2(NC5H3)]}(CO)3(+)Br(-) (1(+)Br(-)) and MnBr{κ(2)-(Ph2P)NMe(NC5H4)}(CO)3 (2), are reported and present new ligand environments for CO2 electrocatalytic reduction to CO. Compound 1(+) presents a unique metal geometry for CO production (96%) in the absence of added water while 2 required addition of water and generated both CO and H2 products.

Capturing Re(i) in an neutral N,N,N pincer Scaffold and resulting enhanced absorption of visible light.

The organometallic and coordination chemistry of rhenium(i) has been largely restricted to bidentate α-diimine ligation and facial tricarbonyl coordination geometries. The thermal transformation of bidentate bis(imino)pyridine and bidentate terpyridine complexes at 200-240 °C under nitrogen led to a family of Re(i) pincer complexes [κ(3)-2,6-{ArN[double bond, length as m-dash]CMe}2(NC5H3)]Re(CO)2X (Ar[double bond, length as m-dash]C6H5, Me2C6H3, (i)Pr2C6H3; X = Cl, Br) and (κ(3)-terpy)Re(CO)2X (X = Cl, Br). The synthesis, single crystal X-ray structural and spectroscopic characterization of these eight species documents their Re coordination geometries and demonstrates the accessibility of such compounds.

Coinage metal complexes supported by a "PN(3)P" scaffold.

A series of monovalent group 11 complexes, [2,6-{Ph2PNMe}2(NC5H3)]CuBr 1, [2,6-{Ph2PNMe}2(NC5H3)]CuOTf 2, [2,6-{Ph2PNMe}2(NC5H3)]AgOTf 3, and [2,6-{Ph2PNMe}2(NC5H3)](AuCl)24, supported by a neutral PN(3)P ligand have been synthesized and characterized by multinuclear NMR and single crystal X-ray diffraction studies. The variation of the coordination properties were analyzed and electronic structure calculations have been carried out to provide insight on the bonding details in these complexes. The Cu(I) complexes displayed an unusual coordination geometry with a tridentate pincer ligand and an overall four coordinate trigonal pyramidal geometry.

The tipping point of the inert pair effect: experimental and computational comparison of In(I) and Sn(II) bis(imino)pyridine complexes.

The autoionization reaction of neutral bis(imino)pyridine and SnX2 led to three compounds [{ArN[double bond, length as m-dash]CPh}2(NC5H3)]SnX(+)SnX3(-) (Ar = 2,6-(2,5-(t)Bu2C6H3), X = Cl, Br; Ar = 2,6-(2,6-Me2C6H3), X = Cl) which display, within the same species, cations and anions possessing Sn(ii) centers. Computational analysis compared the ligated Sn(ii) cations with bis(imino)pyridine In(i) complexes that showed unprecedented weak metal-ligand covalent interactions, consistent with the In(i) 5s(2) electrons remaining as an inert nonbonding pair. Analysis of the metal-ligand bonding indicates that the chloride ligand of the Sn(ii) complex induces promotion of the metal 5s(2) electron pair to a stereochemically active hybridized orbital, which, in turn, allows strong coordination of the bis(imino)pyridine to Sn.

Noncovalent interactions of metal cations and arenes probed with thallium(I) complexes.

The synthesis, characterization, and computational analysis of Tl(I) complexes bearing the bis(imino)pyridine scaffold, [{ArN═CPh}2(NC5H3)]Tl(+)(OTf)(-) (Ar = 2,6-Et2C6H33, 2,5-(t)Bu2C6H3, 4), are reported. The cations of these species showed long Tl-N and Tl-OTf distances indicating only weak or no ligand coordination. Computational analysis of the interactions between the Tl cation and the ligands (orbital populations, bond order, and energy decomposition analysis) point to only minimal covalent interactions of the cation with the ligands.

Solid-state thermolysis of a fac-rhenium(I) carbonyl complex with a redox non-innocent pincer ligand.

The development of rhenium(I) chemistry has been restricted by the limited structural and electronic variability of the common pseudo-octahedral products fac-[ReX(CO)3L2] (L2 = α-diimine). We address this constraint by first preparing the bidentate bis(imino)pyridine complexes [(2,6-{2,6-Me2C6H3N=CPh}2C5H3N)Re(CO)3X] (X = Cl 2, Br 3), which were characterized by spectroscopic and X-ray crystallographic means, and then converting these species into tridentate pincer ligand compounds, [(2,6-{2,6-Me2C6H3N=CPh}2C5H3N)Re(CO)2X] (X = Cl 4, Br 5). This transformation was performed in the solid-state by controlled heating of 2 or 3 above 200 °C in a tube furnace under a flow of nitrogen gas, giving excellent yields (≥95 %).

Bis(N,N',N''-triisopropyl-guanidinium) fumarate-fumaric acid (1/1).

The asymmetric unit of the title compound, C(10)H(24)N(3) (+)·0.5C(4)H(2)O(4) (2-)·0.5C(4)H(4)O(4), comprises a triisopropyl-guanidinium cation, half of a fumarate dianion and half of a fumaric acid mol-ecule; both the fumarate dianion and the fumaric acid mol-ecule are located on inversion centres.

The interplay of metal and supporting ligand in labile coordination to pincer complexes of Ag(I).

The bis(imino)pyridine scaffold provides support for the synthesis and characterization of unique Ag(I) pincer complexes [{ArN=CPh}(2)(NPh)]Ag(+)(OTf)(-) (Ar = 2,5-(t)Bu(2)C(6)H(3)3; 2,6-(i)Pr(2)C(6)H(3) 4). The bonding interactions between the cation-anion and between the bis(imino)pyridine ligand and the Ag centre are presented. Coordination of pyridine, toluene, 2-butyne and cyclooctene to the Ag centre led to the isolation and crystallographic characterization of labile transient adduct species.

N,N',N''-Tricyclo-hexyl-guanidinium iodide.

In the title compound, C(19)H(36)N(3) (+)·I(-), the orientation of the cyclo-hexyl rings around the planar (sum of N-C-N angles = 360°) CN(3) (+) unit produces steric hindrance around the N-H groups. As a consequence of this particular orientation of the tricyclo-hexyl-guanidinium cation (hereafter denoted CHGH(+)), hydrogen bonding is restricted to classical N-H⋯I and non-clasical (cyclo-hex-yl)C-H⋯I hydrogen bonds. The propeller CHGH(+) cation and the oriented hydrogen-bonding interactions lead to a three-dimensional supra-molecular structure.

Single-molecule magnet behavior with a single metal center enhanced through peripheral ligand modifications.

Bis(imino)pyridine pincer ligands in conjunction with two isothiocyanate ligands have been used to prepare two mononuclear Co(II) complexes. Both complexes have a distorted square-pyramidal geometry with the Co(II) centers lying above the basal plane. This leads to significant spin-orbit coupling for the d(7) Co(II) ions and consequently to slow relaxation of the magnetization that is characteristic of Single-Molecule Magnet (SMM) behavior.

Novel pincer complexes of Ag(I), coordination of toluene and their comparison with indium analogues.

The bis(imino)pyridine scaffold provides for the synthesis and characterization of the unique Ag(I) pincer complexes [{ArN=CPh}(2)(NPh)]Ag(+)(OTf)(-) (Ar = 2,5-(t)Bu(2)C(6)H(3); 2,6-(i)Pr(2)C(6)H(3)). The similar covalent radii of Ag(I) and In(I), prompted a bonding comparison of these species with their In(I) analogues. Coordination of toluene to the Ag center revealed the stronger Lewis acidity of the metal site in these compounds relative to In(I) analogues.