David Boston | Colorado State University (original) (raw)

Papers by David Boston

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Sensors and Actuators B: Chemical, 2016

Herein, we first time report Co II bis(terpyridine) complexes as instant 'naked eye' colorimetric... more Herein, we first time report Co II bis(terpyridine) complexes as instant 'naked eye' colorimetric detectors of cyanide (CN-) in micromolar concentration in polar solvents, including water, following formation of the corresponding Co III tricyanide complex. The new Co III tricyanide complex [Co III (4-pyridyl-terpyridine)(CN)3] is characterized by single crystal XRD diffraction. The quanitative detection of cyanide is monitored by UV-Vis spectroscopic method and the selectivety of Co II bis(terpyridine) complexes to the cyanide anion is shown in presence of other anions.

We have investigated catalytic dehydrogenation of glycerol with the goal of converting it to a mo... more We have investigated catalytic dehydrogenation of glycerol with the goal of converting it to a more valuable product. We chose to use Noyori's catalyst to change glycerol to glyceraldehyde. We observed that the reaction rate is slow with few turnovers; this demonstrates a new possible line of research for using glycerol to make other interesting chemicals. By using Ru(TsDPEN)(η 6-cymene), Noyori's catalyst, the chemistry can be shown to work before the catalyst decomposes.

Inorganic Chemistry, 1974

Chemistry - A European Journal, 2015

Four derivatives of the laminate acceptor ligand dipyrido-[3,2-a:2&am... more Four derivatives of the laminate acceptor ligand dipyrido-[3,2-a:2',3'-c]phenazine (dppz) and their corresponding ruthenium complexes, [Ru(phen)2 (dppzX2 )](2+) , were prepared and characterized by NMR spectroscopy, ESI-MS, and elemental analysis. The new ligands, generically denoted dppzX2 , were symmetrically disubstituted on the distal benzene ring to give 10,13-dibromodppz (dppz-p-Br), 11,12-dibromodppz (dppz-o-Br), 10,13-dicyanodppz (dppz-p-CN), 11,12-dicyanodppz (dppz-o-CN). Solvated ground state MO calculations of the ruthenium complexes reveal that these electron-withdrawing substituents not only lower the LUMO of the dppz ligand (dppz(CN)2 <dppzBr2 <dppz), but that the para disubstitution results in a lower LUMO than the ortho disubstitution (dppz-p-CN<(dppz-o-CN), and dppz-p-Br<dppz-o-Br). The validity of the calculations was confirmed experimentally using cyclic voltammetry. Of the complexes evaluated in this study, only the dicyanodppz complexes showed multiple dppz-based reductions prior to reduction of the phen ligands. The capacity to form singly and doubly reduced dppz-based anions at modest reduction potentials was confirmed using a combination of spectroelectrochemical and chemical titration methods. When subjected to photolysis with visible light in the presence of a sacrificial donor, such as triethylamine, both cyano complexes showed multi-electron reduction. The other complexes only show a single reduction.

Energy and Environment Series, 2013

This chapter focuses on the use of molecular catalysts and/or electrode materials (electrocatalyt... more This chapter focuses on the use of molecular catalysts and/or electrode materials (electrocatalytic, semiconductor) to sustain the reduction of CO2. It includes a comparison of molecular catalysts for both electrochemical and photochemical systems as well as a review of the progress made in our own laboratories on semiconductor photocatalysts. Only a few molecular catalysts are capable of deeper reduction than the two-electron reduced products of CO2 (such as CO and formic acid) and the generation of value-added reduction products such as methanol and methane are needed. The challenge to overcome is the overpotential for these electrochemical reactions and short-lived one-electron reduced species for the photochemical systems. Incorporation of a chromophore with the real catalyst in either intermolecular or intramolecular photochemical systems has demonstrated the feasibility of CO2 photoreduction. However, photoinduced electron transfer from the chromophore to the catalyst or from the semiconductor to the solution still account for much of the inefficiency in these systems. Semiconductor-based photocatalyst systems (nanoparticles and electrodes) have shown formation of two-electron reduced products as well as deeper reduction pathways although with limited efficiency. It is our hope that this chapter will contribute to further progress and stimulate future generations of scientists to develop new electro-/photocatalyst design paradigms.

Inorganic Chemistry, 2014

The ruthenium complexes [Ru(phen)2(ptpbα)](2+) (Ruα) and [Ru(phen)2(ptpbβ)](2+) (Ruβ), where phen... more The ruthenium complexes [Ru(phen)2(ptpbα)](2+) (Ruα) and [Ru(phen)2(ptpbβ)](2+) (Ruβ), where phen =1,10-phenanthroline ; ptpbα = pyrido[2',3':5,6]pyrazino[2,3-f][1,10]phenanthroline; ptpbβ = pyrido[3',4':5,6]pyrazino[2,3-f][1,10]phenanthroline, are shown as electrocatalysts and photocatalysts for CO2 reduction to formate, formaldehyde, and methanol. Photochemical activity of both complexes is lost in water but is retained in 1 M H2O in DMF. Controlled current electrolysis of a solution of Ruβ in CO2 saturated DMF:H2O (1 M) yields predominantly methanol over a 6 h period at ∼ -0.60 V versus Ag/AgCl, with traces of formaldehyde. After this time, the potential jumped to -1.15 V producing both methanol and CO as products. Irradiation of Ruβ in a solution of DMF:H2O (1 M) containing 0.2 M TEA (as the sacrificial reductant) yields methanol, formaldehyde, and formate. Identifications of all of the relevant redox and protonated states of the respective complexes were obtained by a combination of voltammetry and differential reflectance measurements. Spectroelectrochemistry was particularly useful to probe the photochemical and electrochemical reduction mechanisms of both complexes as well as the complexes speciation in the absence and presence of CO2.

Journal of the American Chemical Society, 2013

Photochemical catalytic CO2 reduction to formate and methanol has been demonstrated in an aqueous... more Photochemical catalytic CO2 reduction to formate and methanol has been demonstrated in an aqueous homogeneous system at pH 5.0 comprising ruthenium(II) trisphenanthroline as the chromophore, pyridine as the CO2 reduction catalyst, KCl, and ascorbic acid as a sacrificial reductant, using visible light irradiation at 470 ± 20 nm. Isotopic labeling with (13)CO2 yields the six-electron-reduced product (13)CH3OH. After 1 h photolysis, the two-electron-reduced product formate and the six-electron-reduced product methanol are produced with quantum yields of 0.025 and 1.1 × 10(–4), respectively. This represents 76 and 0.15 turnovers per Ru for formate and methanol, respectively, and 152 and 0.9 turnovers per Ru on an electron basis for formate and methanol, respectively. The system is inactive after 6 h irradiation, which appears largely to be due to chromophore degradation. A partial optimization of the methanol yield showed that high pyridine to Ru ratios are needed (100:1) and that the optimum pH is near 5.0. The presence of potassium salts enhances the yield in formate and methanol by 8- and 2-fold, respectively, compared to electrolyte-free solutions; however, other alkali and alkali earth cations have little effect. The addition of small amounts of solid metal catalysts immobilized on carbon had either no effect (M = Pt or Pd) or deleterious effects (M = Ni or Au) on methanol production. Addition of colloidal Pt resulted in no methanol production at all. This is in notable contrast with the pyridine-based electrocatalysis of CO2 to methanol in which metallic or conductive surfaces such as Pt, Pd, or p-type GaP are necessary for methanol formation.

Electrochimica Acta, 1987

Inorganica Chimica Acta, 2016

Abstract A byproduct of the synthesis of 9,11,20,22-tetra-aza-tetrapyrido[3,2-a:2′3′-c:3″,2″-l:2′... more Abstract A byproduct of the synthesis of 9,11,20,22-tetra-aza-tetrapyrido[3,2-a:2′3′-c:3″,2″-l:2′′′,3′′′]-pentacene (tatpp) is the symmetrical dimer ditatpp, which is linked by a carbon-carbon bond along the central benzene ring. The structure of the dimer has been determined by X-ray crystallography and reveals a dihedral angle of 73° between the two tatpp units, which is likely due lone pair repulsion on the adjacent aza nitrogens on each tatpp unit. Because of this non-planar geometry, this ditatpp dimer is freely soluble in organic solvents, such as ethanol, very much unlike the tatpp ligand, which is sparingly soluble in all common solvents. Photolysis of ditatpp with visible light in the presence of sacrificial donors, such as triethylamine, results in multi-electron reduction on each of the tatpp units, as determined by absorption spectroscopy. As the tatpp units appear to function independently of one another, and each tatpp unit is reduced by two electrons and is doubly protonated in the final compound, the photoreduction results in a net storage of 4 electrons in the fully reduced species.

The dinuclear ruthenium(II) complex [(phen) 2 Ru(tatpOMe)Ru(phen) 2 ] 4+ (2 4+ ; phen is 1,10-phe... more The dinuclear ruthenium(II) complex [(phen) 2 Ru(tatpOMe)Ru(phen) 2 ] 4+ (2 4+ ; phen is 1,10-phenanthroline and tatpOMe is 10,21-dimethoxy-9,10,20,33-tetraazatetrapyrido[3,2-a:2¢3¢c:3¢¢,2¢¢-l:2¢¢¢,3¢¢¢-n]pentacene) has been synthesized and characterized by 1 H NMR, ESI mass spectroscopy and elemental analysis. Loss of methoxy group from bridging ligand of complex 2 4+ due to irradiation is observed by 1 H NMR and photochemistry. The interrelated electronic properties UV-Vis, electrochemistry, photochemistry and molecular orbital calculation are analyzed and discussed on the bridging ligand of the complex 2 4+ .

Please note that technical editing may introduce minor changes to the text and/or graphics, which... more Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal's standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Sensors and Actuators B: Chemical, 2016

Herein, we first time report Co II bis(terpyridine) complexes as instant 'naked eye' colorimetric... more Herein, we first time report Co II bis(terpyridine) complexes as instant 'naked eye' colorimetric detectors of cyanide (CN-) in micromolar concentration in polar solvents, including water, following formation of the corresponding Co III tricyanide complex. The new Co III tricyanide complex [Co III (4-pyridyl-terpyridine)(CN)3] is characterized by single crystal XRD diffraction. The quanitative detection of cyanide is monitored by UV-Vis spectroscopic method and the selectivety of Co II bis(terpyridine) complexes to the cyanide anion is shown in presence of other anions.

We have investigated catalytic dehydrogenation of glycerol with the goal of converting it to a mo... more We have investigated catalytic dehydrogenation of glycerol with the goal of converting it to a more valuable product. We chose to use Noyori's catalyst to change glycerol to glyceraldehyde. We observed that the reaction rate is slow with few turnovers; this demonstrates a new possible line of research for using glycerol to make other interesting chemicals. By using Ru(TsDPEN)(η 6-cymene), Noyori's catalyst, the chemistry can be shown to work before the catalyst decomposes.

Inorganic Chemistry, 1974

Chemistry - A European Journal, 2015

Four derivatives of the laminate acceptor ligand dipyrido-[3,2-a:2&am... more Four derivatives of the laminate acceptor ligand dipyrido-[3,2-a:2',3'-c]phenazine (dppz) and their corresponding ruthenium complexes, [Ru(phen)2 (dppzX2 )](2+) , were prepared and characterized by NMR spectroscopy, ESI-MS, and elemental analysis. The new ligands, generically denoted dppzX2 , were symmetrically disubstituted on the distal benzene ring to give 10,13-dibromodppz (dppz-p-Br), 11,12-dibromodppz (dppz-o-Br), 10,13-dicyanodppz (dppz-p-CN), 11,12-dicyanodppz (dppz-o-CN). Solvated ground state MO calculations of the ruthenium complexes reveal that these electron-withdrawing substituents not only lower the LUMO of the dppz ligand (dppz(CN)2 <dppzBr2 <dppz), but that the para disubstitution results in a lower LUMO than the ortho disubstitution (dppz-p-CN<(dppz-o-CN), and dppz-p-Br<dppz-o-Br). The validity of the calculations was confirmed experimentally using cyclic voltammetry. Of the complexes evaluated in this study, only the dicyanodppz complexes showed multiple dppz-based reductions prior to reduction of the phen ligands. The capacity to form singly and doubly reduced dppz-based anions at modest reduction potentials was confirmed using a combination of spectroelectrochemical and chemical titration methods. When subjected to photolysis with visible light in the presence of a sacrificial donor, such as triethylamine, both cyano complexes showed multi-electron reduction. The other complexes only show a single reduction.

Energy and Environment Series, 2013

This chapter focuses on the use of molecular catalysts and/or electrode materials (electrocatalyt... more This chapter focuses on the use of molecular catalysts and/or electrode materials (electrocatalytic, semiconductor) to sustain the reduction of CO2. It includes a comparison of molecular catalysts for both electrochemical and photochemical systems as well as a review of the progress made in our own laboratories on semiconductor photocatalysts. Only a few molecular catalysts are capable of deeper reduction than the two-electron reduced products of CO2 (such as CO and formic acid) and the generation of value-added reduction products such as methanol and methane are needed. The challenge to overcome is the overpotential for these electrochemical reactions and short-lived one-electron reduced species for the photochemical systems. Incorporation of a chromophore with the real catalyst in either intermolecular or intramolecular photochemical systems has demonstrated the feasibility of CO2 photoreduction. However, photoinduced electron transfer from the chromophore to the catalyst or from the semiconductor to the solution still account for much of the inefficiency in these systems. Semiconductor-based photocatalyst systems (nanoparticles and electrodes) have shown formation of two-electron reduced products as well as deeper reduction pathways although with limited efficiency. It is our hope that this chapter will contribute to further progress and stimulate future generations of scientists to develop new electro-/photocatalyst design paradigms.

Inorganic Chemistry, 2014

The ruthenium complexes [Ru(phen)2(ptpbα)](2+) (Ruα) and [Ru(phen)2(ptpbβ)](2+) (Ruβ), where phen... more The ruthenium complexes [Ru(phen)2(ptpbα)](2+) (Ruα) and [Ru(phen)2(ptpbβ)](2+) (Ruβ), where phen =1,10-phenanthroline ; ptpbα = pyrido[2',3':5,6]pyrazino[2,3-f][1,10]phenanthroline; ptpbβ = pyrido[3',4':5,6]pyrazino[2,3-f][1,10]phenanthroline, are shown as electrocatalysts and photocatalysts for CO2 reduction to formate, formaldehyde, and methanol. Photochemical activity of both complexes is lost in water but is retained in 1 M H2O in DMF. Controlled current electrolysis of a solution of Ruβ in CO2 saturated DMF:H2O (1 M) yields predominantly methanol over a 6 h period at ∼ -0.60 V versus Ag/AgCl, with traces of formaldehyde. After this time, the potential jumped to -1.15 V producing both methanol and CO as products. Irradiation of Ruβ in a solution of DMF:H2O (1 M) containing 0.2 M TEA (as the sacrificial reductant) yields methanol, formaldehyde, and formate. Identifications of all of the relevant redox and protonated states of the respective complexes were obtained by a combination of voltammetry and differential reflectance measurements. Spectroelectrochemistry was particularly useful to probe the photochemical and electrochemical reduction mechanisms of both complexes as well as the complexes speciation in the absence and presence of CO2.

Journal of the American Chemical Society, 2013

Photochemical catalytic CO2 reduction to formate and methanol has been demonstrated in an aqueous... more Photochemical catalytic CO2 reduction to formate and methanol has been demonstrated in an aqueous homogeneous system at pH 5.0 comprising ruthenium(II) trisphenanthroline as the chromophore, pyridine as the CO2 reduction catalyst, KCl, and ascorbic acid as a sacrificial reductant, using visible light irradiation at 470 ± 20 nm. Isotopic labeling with (13)CO2 yields the six-electron-reduced product (13)CH3OH. After 1 h photolysis, the two-electron-reduced product formate and the six-electron-reduced product methanol are produced with quantum yields of 0.025 and 1.1 × 10(–4), respectively. This represents 76 and 0.15 turnovers per Ru for formate and methanol, respectively, and 152 and 0.9 turnovers per Ru on an electron basis for formate and methanol, respectively. The system is inactive after 6 h irradiation, which appears largely to be due to chromophore degradation. A partial optimization of the methanol yield showed that high pyridine to Ru ratios are needed (100:1) and that the optimum pH is near 5.0. The presence of potassium salts enhances the yield in formate and methanol by 8- and 2-fold, respectively, compared to electrolyte-free solutions; however, other alkali and alkali earth cations have little effect. The addition of small amounts of solid metal catalysts immobilized on carbon had either no effect (M = Pt or Pd) or deleterious effects (M = Ni or Au) on methanol production. Addition of colloidal Pt resulted in no methanol production at all. This is in notable contrast with the pyridine-based electrocatalysis of CO2 to methanol in which metallic or conductive surfaces such as Pt, Pd, or p-type GaP are necessary for methanol formation.

Electrochimica Acta, 1987

Inorganica Chimica Acta, 2016

Abstract A byproduct of the synthesis of 9,11,20,22-tetra-aza-tetrapyrido[3,2-a:2′3′-c:3″,2″-l:2′... more Abstract A byproduct of the synthesis of 9,11,20,22-tetra-aza-tetrapyrido[3,2-a:2′3′-c:3″,2″-l:2′′′,3′′′]-pentacene (tatpp) is the symmetrical dimer ditatpp, which is linked by a carbon-carbon bond along the central benzene ring. The structure of the dimer has been determined by X-ray crystallography and reveals a dihedral angle of 73° between the two tatpp units, which is likely due lone pair repulsion on the adjacent aza nitrogens on each tatpp unit. Because of this non-planar geometry, this ditatpp dimer is freely soluble in organic solvents, such as ethanol, very much unlike the tatpp ligand, which is sparingly soluble in all common solvents. Photolysis of ditatpp with visible light in the presence of sacrificial donors, such as triethylamine, results in multi-electron reduction on each of the tatpp units, as determined by absorption spectroscopy. As the tatpp units appear to function independently of one another, and each tatpp unit is reduced by two electrons and is doubly protonated in the final compound, the photoreduction results in a net storage of 4 electrons in the fully reduced species.

The dinuclear ruthenium(II) complex [(phen) 2 Ru(tatpOMe)Ru(phen) 2 ] 4+ (2 4+ ; phen is 1,10-phe... more The dinuclear ruthenium(II) complex [(phen) 2 Ru(tatpOMe)Ru(phen) 2 ] 4+ (2 4+ ; phen is 1,10-phenanthroline and tatpOMe is 10,21-dimethoxy-9,10,20,33-tetraazatetrapyrido[3,2-a:2¢3¢c:3¢¢,2¢¢-l:2¢¢¢,3¢¢¢-n]pentacene) has been synthesized and characterized by 1 H NMR, ESI mass spectroscopy and elemental analysis. Loss of methoxy group from bridging ligand of complex 2 4+ due to irradiation is observed by 1 H NMR and photochemistry. The interrelated electronic properties UV-Vis, electrochemistry, photochemistry and molecular orbital calculation are analyzed and discussed on the bridging ligand of the complex 2 4+ .

Please note that technical editing may introduce minor changes to the text and/or graphics, which... more Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal's standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.