Bret Johnson | College of St Scholastica (original) (raw)
Papers by Bret Johnson
Acta Crystallographica Section C Crystal Structure Communications
Acta Crystallographica Section C. Crystal Structure Communications. 0108-2701. metal-organic comp... more Acta Crystallographica Section C. Crystal Structure Communications. 0108-2701. metal-organic compounds. Volume 55 Part 4 Pages 549-551 April 1999 Tetrakis(tetrabutylammonium) tetrakis[(p-cyanophenyl)trioxoarsonato]tetratriacontaoxododecamolybdate(4 -). ...
Inorganic Chemistry, 2002
Polyoxometalate (POM) clusters derivatized with aniline groups exhibit distinct interactions with... more Polyoxometalate (POM) clusters derivatized with aniline groups exhibit distinct interactions with counterions and with each other. These interactions lead to the assembly of the clusters into chains and networks upon crystallization. Two cluster types were examined, [W 6 O 25 H(AsC 6 H 4-4-NH 2) 2 ] 5and [Mo 12 O 46 (AsC 6 H 4-4-NH 2) 4 ] 4-. The X-ray crystal structures were solved for the mixed salts containing [C(NH 2) 3 ] + /Na + , Ag + /H + , or Cu 2+ /H + as counterions. The X-ray crystal structures reveal that the POM clusters are linked together by hydrogen bonds or POM−metal ion−POM linkages. The roles of the counterions, solvents, and organic groups in the formation of specific crystalline architectures are discussed. Strongly interacting counterions form bonds to the oxo ligands of the POM and connect them into tetrameric units and/or into one-dimensional chains. The hydrogen bonding strength of the solvent influences the formation of hydrogen bonds between the aniline groups and oxo ligands of the cluster. The aniline groups played differing roles in the final structures: they were either nonbonding, bonded to a counterion, or involved in hydrogen bonding. Depending on the bonding interactions, the architecture of the cluster salts may be significantly altered.
Inorganic Chemistry, 2001
New organic derivatives of "inverse-Keggin" polyoxometalate (POM) clusters, [Mo 12 O 46 (AsR) 4 ]... more New organic derivatives of "inverse-Keggin" polyoxometalate (POM) clusters, [Mo 12 O 46 (AsR) 4 ] 4-(R) C 6 H 4-4-COOH, C 6 H 3-4-OH-3-NO 2 , C 6 H 4-4-OH), have been synthesized. Structures of the corresponding sodium or iron salts were elucidated by single-crystal X-ray diffraction and shown to be 3D structures connected through hydrogen bonds and/or O-Na-O linkages. Parameters which influence the final solid-state architecture, such as the crystallizing solvent, organic moiety, and counterions, have been examined. The hydrogen-bonding ability of the solvent affects the connectivity of the POM clusters through interactions with the organic group and the inorganic core. The organic groups influence the structure through hydrogen bonds to other organic groups, to neighboring clusters, and/or to solvent molecules. Hydrogen bonding between the organic groups and the solvent appears to inhibit some possible connectivity patterns, such as the hydrogen-bonded dimerization of carboxylic acid groups. Na + ions were found directly bonded to the cluster oxo ligands and provided linkages between clusters. Larger cations, such as transition metals, did not show this interaction, and other bonding methods dominated.
Inorganic Chemistry, 2001
Transition-metal-substituted polyoxometalates (TMSP) of the type [MII(H2O)PW11O39]5- (M = Co, Zn)... more Transition-metal-substituted polyoxometalates (TMSP) of the type [MII(H2O)PW11O39]5- (M = Co, Zn) and [SiW9O37(CoII(H2O))3]10- have been chemically anchored to modified macroporous (400 nm pores), mesoporous (2.8 nm pores), and amorphous silica surfaces. The materials were characterized by solid-state 31P MAS NMR, UV-vis, FT-IR spectroscopy, and N2 adsorption experiments to verify cluster attachment and the structure of the TMSP on the support. On the basis of the spectroscopic evidence, clusters were attached datively to the surface, and the integrity of the [CoPW11] cluster was maintained for nonaqueous impregnation with TBA5[CoPW11]; partial degradation of the cluster occurred when it was impregnated from aqueous solution using the K5[CoPW11] salt. Both the amine surface groups and the cobalt centers in the clusters were found to be necessary to prevent cluster loss during washing or reaction processes. The catalytic activities of the supported TMSP clusters were tested by the epoxidation of cyclohexene to cyclohexene oxide in the presence of isobutyraldehyde. The percent conversion of the substrate and the amount of product formed per unit time were similar for [CoPW11] clusters on each of the three silica supports, but slightly lower than for purely homogeneous reactions. [SiW9Co3] clusters with three available cobalt centers exhibited higher catalytic activity with nearly identical performance on a silica support or in homogeneous solution.
Dalton Transactions, 2003
Dalton Trans., 2003, 4678-4681 DOI:10.1039/B309453G (Paper). A coordination network containing no... more Dalton Trans., 2003, 4678-4681 DOI:10.1039/B309453G (Paper). A coordination network containing non-coordinating polyoxometalate clusters as counterions. Bret JS Johnson, Sarah A. Geers, William W. Brennessel, Victor G. Young, Jr. ...
Chemistry of Materials, 2001
Three-dimensionally ordered macroporous (3DOM) silica materials functionalized with highly disper... more Three-dimensionally ordered macroporous (3DOM) silica materials functionalized with highly dispersed polyoxometalate clusters have been prepared via direct synthesis. Lacunary γ-decatungstosilicate clusters were incorporated into the wall structures of macroporous silica by reaction of the clusters in acidic solution with tetraethoxysilane, with or without addition of the polyfunctional linking group 1,2-bis(triethoxysilyl)ethane, followed by condensation around polystyrene colloidal crystals. Removal of the polystyrene template by extraction with a tetrahydrofuran/acetone solution produced the porous hybrid materials. The products were characterized by IR, solid-state 29Si and 13C NMR, scanning electron microscopy (SEM), transmission electron microscopy, X-ray energy-dispersive spectroscopy, and chemical analysis. The polyoxometalate clusters remained intact in the hybrid structures and were nearly molecularly dispersed throughout the walls of the 3DOM materials. High incorporation levels of cluster were...
Inorganic …, 2002
Polyoxometalate (POM) clusters derivatized with aniline groups exhibit distinct interactions with... more Polyoxometalate (POM) clusters derivatized with aniline groups exhibit distinct interactions with counterions and with each other. These interactions lead to the assembly of the clusters into chains and networks upon crystallization. Two cluster types were examined, [W 6 O 25 H(AsC 6 H 4-4-NH 2) 2 ] 5and [Mo 12 O 46 (AsC 6 H 4-4-NH 2) 4 ] 4-. The X-ray crystal structures were solved for the mixed salts containing [C(NH 2) 3 ] + /Na + , Ag + /H + , or Cu 2+ /H + as counterions. The X-ray crystal structures reveal that the POM clusters are linked together by hydrogen bonds or POM−metal ion−POM linkages. The roles of the counterions, solvents, and organic groups in the formation of specific crystalline architectures are discussed. Strongly interacting counterions form bonds to the oxo ligands of the POM and connect them into tetrameric units and/or into one-dimensional chains. The hydrogen bonding strength of the solvent influences the formation of hydrogen bonds between the aniline groups and oxo ligands of the cluster. The aniline groups played differing roles in the final structures: they were either nonbonding, bonded to a counterion, or involved in hydrogen bonding. Depending on the bonding interactions, the architecture of the cluster salts may be significantly altered.
Dalton Trans., 2003
Dalton Trans., 2003, 4678-4681 DOI:10.1039/B309453G (Paper). A coordination network containing no... more Dalton Trans., 2003, 4678-4681 DOI:10.1039/B309453G (Paper). A coordination network containing non-coordinating polyoxometalate clusters as counterions. Bret JS Johnson, Sarah A. Geers, William W. Brennessel, Victor G. Young, Jr. ...
Inorganic Chemistry, 2001
New organic derivatives of "inverse-Keggin" polyoxometalate (POM) clusters, [Mo 12 O 46 (AsR) 4 ]... more New organic derivatives of "inverse-Keggin" polyoxometalate (POM) clusters, [Mo 12 O 46 (AsR) 4 ] 4-(R) C 6 H 4-4-COOH, C 6 H 3-4-OH-3-NO 2 , C 6 H 4-4-OH), have been synthesized. Structures of the corresponding sodium or iron salts were elucidated by single-crystal X-ray diffraction and shown to be 3D structures connected through hydrogen bonds and/or O-Na-O linkages. Parameters which influence the final solid-state architecture, such as the crystallizing solvent, organic moiety, and counterions, have been examined. The hydrogen-bonding ability of the solvent affects the connectivity of the POM clusters through interactions with the organic group and the inorganic core. The organic groups influence the structure through hydrogen bonds to other organic groups, to neighboring clusters, and/or to solvent molecules. Hydrogen bonding between the organic groups and the solvent appears to inhibit some possible connectivity patterns, such as the hydrogen-bonded dimerization of carboxylic acid groups. Na + ions were found directly bonded to the cluster oxo ligands and provided linkages between clusters. Larger cations, such as transition metals, did not show this interaction, and other bonding methods dominated.
Faraday Discuss., 2004
Faraday Discuss., 2005, 128, 149-162 DOI:10.1039/B403217A (Paper). Control of pore hydrophilicity... more Faraday Discuss., 2005, 128, 149-162 DOI:10.1039/B403217A (Paper). Control of pore hydrophilicity in ordered nanoporous polystyrene using an AB/AC block copolymer blending strategy. Huiming Mao, Pedro L. Arrechea, Travis ...
Inorganic Chemistry, 2001
Transition-metal-substituted polyoxometalates (TMSP) of the type [MII(H2O)PW11O39]5- (M = Co, Zn)... more Transition-metal-substituted polyoxometalates (TMSP) of the type [MII(H2O)PW11O39]5- (M = Co, Zn) and [SiW9O37(CoII(H2O))3]10- have been chemically anchored to modified macroporous (400 nm pores), mesoporous (2.8 nm pores), and amorphous silica surfaces. The materials were characterized by solid-state 31P MAS NMR, UV-vis, FT-IR spectroscopy, and N2 adsorption experiments to verify cluster attachment and the structure of the TMSP on the support. On the basis of the spectroscopic evidence, clusters were attached datively to the surface, and the integrity of the [CoPW11] cluster was maintained for nonaqueous impregnation with TBA5[CoPW11]; partial degradation of the cluster occurred when it was impregnated from aqueous solution using the K5[CoPW11] salt. Both the amine surface groups and the cobalt centers in the clusters were found to be necessary to prevent cluster loss during washing or reaction processes. The catalytic activities of the supported TMSP clusters were tested by the epoxidation of cyclohexene to cyclohexene oxide in the presence of isobutyraldehyde. The percent conversion of the substrate and the amount of product formed per unit time were similar for [CoPW11] clusters on each of the three silica supports, but slightly lower than for purely homogeneous reactions. [SiW9Co3] clusters with three available cobalt centers exhibited higher catalytic activity with nearly identical performance on a silica support or in homogeneous solution.
Chemistry of …, 2004
... Bret JS Johnson, Johanna H. Wolf, Andrew S. Zalusky, and Marc A. Hillmyer*. Department of Che... more ... Bret JS Johnson, Johanna H. Wolf, Andrew S. Zalusky, and Marc A. Hillmyer*. Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431. Chem. Mater. ... The longest reaction time resulted in the most PPY filling, ca. ...
Acta Crystallographica Section C Crystal Structure Communications
Acta Crystallographica Section C. Crystal Structure Communications. 0108-2701. metal-organic comp... more Acta Crystallographica Section C. Crystal Structure Communications. 0108-2701. metal-organic compounds. Volume 55 Part 4 Pages 549-551 April 1999 Tetrakis(tetrabutylammonium) tetrakis[(p-cyanophenyl)trioxoarsonato]tetratriacontaoxododecamolybdate(4 -). ...
Inorganic Chemistry, 2002
Polyoxometalate (POM) clusters derivatized with aniline groups exhibit distinct interactions with... more Polyoxometalate (POM) clusters derivatized with aniline groups exhibit distinct interactions with counterions and with each other. These interactions lead to the assembly of the clusters into chains and networks upon crystallization. Two cluster types were examined, [W 6 O 25 H(AsC 6 H 4-4-NH 2) 2 ] 5and [Mo 12 O 46 (AsC 6 H 4-4-NH 2) 4 ] 4-. The X-ray crystal structures were solved for the mixed salts containing [C(NH 2) 3 ] + /Na + , Ag + /H + , or Cu 2+ /H + as counterions. The X-ray crystal structures reveal that the POM clusters are linked together by hydrogen bonds or POM−metal ion−POM linkages. The roles of the counterions, solvents, and organic groups in the formation of specific crystalline architectures are discussed. Strongly interacting counterions form bonds to the oxo ligands of the POM and connect them into tetrameric units and/or into one-dimensional chains. The hydrogen bonding strength of the solvent influences the formation of hydrogen bonds between the aniline groups and oxo ligands of the cluster. The aniline groups played differing roles in the final structures: they were either nonbonding, bonded to a counterion, or involved in hydrogen bonding. Depending on the bonding interactions, the architecture of the cluster salts may be significantly altered.
Inorganic Chemistry, 2001
New organic derivatives of "inverse-Keggin" polyoxometalate (POM) clusters, [Mo 12 O 46 (AsR) 4 ]... more New organic derivatives of "inverse-Keggin" polyoxometalate (POM) clusters, [Mo 12 O 46 (AsR) 4 ] 4-(R) C 6 H 4-4-COOH, C 6 H 3-4-OH-3-NO 2 , C 6 H 4-4-OH), have been synthesized. Structures of the corresponding sodium or iron salts were elucidated by single-crystal X-ray diffraction and shown to be 3D structures connected through hydrogen bonds and/or O-Na-O linkages. Parameters which influence the final solid-state architecture, such as the crystallizing solvent, organic moiety, and counterions, have been examined. The hydrogen-bonding ability of the solvent affects the connectivity of the POM clusters through interactions with the organic group and the inorganic core. The organic groups influence the structure through hydrogen bonds to other organic groups, to neighboring clusters, and/or to solvent molecules. Hydrogen bonding between the organic groups and the solvent appears to inhibit some possible connectivity patterns, such as the hydrogen-bonded dimerization of carboxylic acid groups. Na + ions were found directly bonded to the cluster oxo ligands and provided linkages between clusters. Larger cations, such as transition metals, did not show this interaction, and other bonding methods dominated.
Inorganic Chemistry, 2001
Transition-metal-substituted polyoxometalates (TMSP) of the type [MII(H2O)PW11O39]5- (M = Co, Zn)... more Transition-metal-substituted polyoxometalates (TMSP) of the type [MII(H2O)PW11O39]5- (M = Co, Zn) and [SiW9O37(CoII(H2O))3]10- have been chemically anchored to modified macroporous (400 nm pores), mesoporous (2.8 nm pores), and amorphous silica surfaces. The materials were characterized by solid-state 31P MAS NMR, UV-vis, FT-IR spectroscopy, and N2 adsorption experiments to verify cluster attachment and the structure of the TMSP on the support. On the basis of the spectroscopic evidence, clusters were attached datively to the surface, and the integrity of the [CoPW11] cluster was maintained for nonaqueous impregnation with TBA5[CoPW11]; partial degradation of the cluster occurred when it was impregnated from aqueous solution using the K5[CoPW11] salt. Both the amine surface groups and the cobalt centers in the clusters were found to be necessary to prevent cluster loss during washing or reaction processes. The catalytic activities of the supported TMSP clusters were tested by the epoxidation of cyclohexene to cyclohexene oxide in the presence of isobutyraldehyde. The percent conversion of the substrate and the amount of product formed per unit time were similar for [CoPW11] clusters on each of the three silica supports, but slightly lower than for purely homogeneous reactions. [SiW9Co3] clusters with three available cobalt centers exhibited higher catalytic activity with nearly identical performance on a silica support or in homogeneous solution.
Dalton Transactions, 2003
Dalton Trans., 2003, 4678-4681 DOI:10.1039/B309453G (Paper). A coordination network containing no... more Dalton Trans., 2003, 4678-4681 DOI:10.1039/B309453G (Paper). A coordination network containing non-coordinating polyoxometalate clusters as counterions. Bret JS Johnson, Sarah A. Geers, William W. Brennessel, Victor G. Young, Jr. ...
Chemistry of Materials, 2001
Three-dimensionally ordered macroporous (3DOM) silica materials functionalized with highly disper... more Three-dimensionally ordered macroporous (3DOM) silica materials functionalized with highly dispersed polyoxometalate clusters have been prepared via direct synthesis. Lacunary γ-decatungstosilicate clusters were incorporated into the wall structures of macroporous silica by reaction of the clusters in acidic solution with tetraethoxysilane, with or without addition of the polyfunctional linking group 1,2-bis(triethoxysilyl)ethane, followed by condensation around polystyrene colloidal crystals. Removal of the polystyrene template by extraction with a tetrahydrofuran/acetone solution produced the porous hybrid materials. The products were characterized by IR, solid-state 29Si and 13C NMR, scanning electron microscopy (SEM), transmission electron microscopy, X-ray energy-dispersive spectroscopy, and chemical analysis. The polyoxometalate clusters remained intact in the hybrid structures and were nearly molecularly dispersed throughout the walls of the 3DOM materials. High incorporation levels of cluster were...
Inorganic …, 2002
Polyoxometalate (POM) clusters derivatized with aniline groups exhibit distinct interactions with... more Polyoxometalate (POM) clusters derivatized with aniline groups exhibit distinct interactions with counterions and with each other. These interactions lead to the assembly of the clusters into chains and networks upon crystallization. Two cluster types were examined, [W 6 O 25 H(AsC 6 H 4-4-NH 2) 2 ] 5and [Mo 12 O 46 (AsC 6 H 4-4-NH 2) 4 ] 4-. The X-ray crystal structures were solved for the mixed salts containing [C(NH 2) 3 ] + /Na + , Ag + /H + , or Cu 2+ /H + as counterions. The X-ray crystal structures reveal that the POM clusters are linked together by hydrogen bonds or POM−metal ion−POM linkages. The roles of the counterions, solvents, and organic groups in the formation of specific crystalline architectures are discussed. Strongly interacting counterions form bonds to the oxo ligands of the POM and connect them into tetrameric units and/or into one-dimensional chains. The hydrogen bonding strength of the solvent influences the formation of hydrogen bonds between the aniline groups and oxo ligands of the cluster. The aniline groups played differing roles in the final structures: they were either nonbonding, bonded to a counterion, or involved in hydrogen bonding. Depending on the bonding interactions, the architecture of the cluster salts may be significantly altered.
Dalton Trans., 2003
Dalton Trans., 2003, 4678-4681 DOI:10.1039/B309453G (Paper). A coordination network containing no... more Dalton Trans., 2003, 4678-4681 DOI:10.1039/B309453G (Paper). A coordination network containing non-coordinating polyoxometalate clusters as counterions. Bret JS Johnson, Sarah A. Geers, William W. Brennessel, Victor G. Young, Jr. ...
Inorganic Chemistry, 2001
New organic derivatives of "inverse-Keggin" polyoxometalate (POM) clusters, [Mo 12 O 46 (AsR) 4 ]... more New organic derivatives of "inverse-Keggin" polyoxometalate (POM) clusters, [Mo 12 O 46 (AsR) 4 ] 4-(R) C 6 H 4-4-COOH, C 6 H 3-4-OH-3-NO 2 , C 6 H 4-4-OH), have been synthesized. Structures of the corresponding sodium or iron salts were elucidated by single-crystal X-ray diffraction and shown to be 3D structures connected through hydrogen bonds and/or O-Na-O linkages. Parameters which influence the final solid-state architecture, such as the crystallizing solvent, organic moiety, and counterions, have been examined. The hydrogen-bonding ability of the solvent affects the connectivity of the POM clusters through interactions with the organic group and the inorganic core. The organic groups influence the structure through hydrogen bonds to other organic groups, to neighboring clusters, and/or to solvent molecules. Hydrogen bonding between the organic groups and the solvent appears to inhibit some possible connectivity patterns, such as the hydrogen-bonded dimerization of carboxylic acid groups. Na + ions were found directly bonded to the cluster oxo ligands and provided linkages between clusters. Larger cations, such as transition metals, did not show this interaction, and other bonding methods dominated.
Faraday Discuss., 2004
Faraday Discuss., 2005, 128, 149-162 DOI:10.1039/B403217A (Paper). Control of pore hydrophilicity... more Faraday Discuss., 2005, 128, 149-162 DOI:10.1039/B403217A (Paper). Control of pore hydrophilicity in ordered nanoporous polystyrene using an AB/AC block copolymer blending strategy. Huiming Mao, Pedro L. Arrechea, Travis ...
Inorganic Chemistry, 2001
Transition-metal-substituted polyoxometalates (TMSP) of the type [MII(H2O)PW11O39]5- (M = Co, Zn)... more Transition-metal-substituted polyoxometalates (TMSP) of the type [MII(H2O)PW11O39]5- (M = Co, Zn) and [SiW9O37(CoII(H2O))3]10- have been chemically anchored to modified macroporous (400 nm pores), mesoporous (2.8 nm pores), and amorphous silica surfaces. The materials were characterized by solid-state 31P MAS NMR, UV-vis, FT-IR spectroscopy, and N2 adsorption experiments to verify cluster attachment and the structure of the TMSP on the support. On the basis of the spectroscopic evidence, clusters were attached datively to the surface, and the integrity of the [CoPW11] cluster was maintained for nonaqueous impregnation with TBA5[CoPW11]; partial degradation of the cluster occurred when it was impregnated from aqueous solution using the K5[CoPW11] salt. Both the amine surface groups and the cobalt centers in the clusters were found to be necessary to prevent cluster loss during washing or reaction processes. The catalytic activities of the supported TMSP clusters were tested by the epoxidation of cyclohexene to cyclohexene oxide in the presence of isobutyraldehyde. The percent conversion of the substrate and the amount of product formed per unit time were similar for [CoPW11] clusters on each of the three silica supports, but slightly lower than for purely homogeneous reactions. [SiW9Co3] clusters with three available cobalt centers exhibited higher catalytic activity with nearly identical performance on a silica support or in homogeneous solution.
Chemistry of …, 2004
... Bret JS Johnson, Johanna H. Wolf, Andrew S. Zalusky, and Marc A. Hillmyer*. Department of Che... more ... Bret JS Johnson, Johanna H. Wolf, Andrew S. Zalusky, and Marc A. Hillmyer*. Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431. Chem. Mater. ... The longest reaction time resulted in the most PPY filling, ca. ...