The Experts below are selected from a list of 774 Experts worldwide ranked by ideXlab platform
Dario Pasini - One of the best experts on this subject based on the ideXlab platform.
-
from red to blue shift switching the binding affinity from the acceptor to the donor end by increasing the π bridge in push pull chromophores with coordinative ends
New Journal of Chemistry, 2013Co-Authors: Marco Caricato, Carmine Coluccini, Alessandra Forni, Douglas Vander A Griend, Dario PasiniAbstract:A series of homologous push–pull compounds, in which identical donor (a dimethylamino) and acceptor (a Malonate Ester) functionalities endcap crescent PPV fragments, exhibit striking differences in their supramolecular recognition of cations acting as Lewis acids. The shorter conjugated compound (one phenyl ring) coordinates a wide variety of lanthanide cations (Eu3+, Yb3+ and Er3+) in MeCN solutions to the 1,3-dicarbonyl acceptor end, resulting in an overall supramolecular polarization of the system (red shift of the intramolecular charge-transfer ICT band). With the “hard” cation Sc3+, recognition switches to the tertiary amine donor end, turning the conjugated system from D–π–A to A–π–A, and resulting in a blue shift of the ICT band upon complexation. Interestingly, increasing the conjugation by means of the insertion of sequential p-phenylenevinylene units into the ligand results in coordination to the donor end regardless of cation “hardness” (Sc3+, Eu3+ and Er3+), suggesting a relative change in the nucleophilicity of the two coordinating ends when increasing the length of the conjugated π-bridge. Such a hypothesis is supported by quantum chemical calculations on the ligands and subsequent atomic charges determination using two independent approaches (QTAIM and CHelpG). The characterization of the thermodynamic stabilities and the dimensionalities of the ligand–cation complexes in solution reveals striking differences from case to case, yet increasing affinities (from log Kav = 2.5 to log Kav = 4.9) are recorded with the increase of the π-conjugated bridge.
-
switching of emissive and nlo properties in push pull chromophores with crescent ppv like structures
Physical Chemistry Chemical Physics, 2013Co-Authors: Carmine Coluccini, Arvind K Sharma, Marco Caricato, Angelo Sironi, Elena Cariati, Stefania Righetto, Elisa Tordin, Chiara Botta, Alessandra Forni, Dario PasiniAbstract:We report on a series of novel homologous push–pull compounds, in which identical donor (a dimethylamino) and acceptor (a Malonate Ester) functionalities endcap crescent PPV fragments, bearing, respectively, 1, 2 and 3 p-phenylenevinylene units in direct linear conjugation (compounds 7–9). The three compounds exhibit striking differences in their linear and nonlinear optical properties. The shorter compound 7 exhibits aggregation-induced emission with a strong luminescence in the solid state (blue emission, photoluminescence quantum yield 38%), and it is nonemissive in solution; the more extended conjugated systems 8 and 9 show classical aggregation-caused quenching in the solid state, while high quantum yield photoluminescence (21 and 93% in toluene) is restored in diluted solutions, through mechanisms involving intramolecular charge transfer in the excited states. EFISH measurements in solutions demonstrate a strong solvent and concentration dependence. As rationalized with the aid of molecular modelling, compounds 8 and, more markedly, 9 aggregate in stable centrosymmetric dimers in solution.
Carmine Coluccini - One of the best experts on this subject based on the ideXlab platform.
-
from red to blue shift switching the binding affinity from the acceptor to the donor end by increasing the π bridge in push pull chromophores with coordinative ends
New Journal of Chemistry, 2013Co-Authors: Marco Caricato, Carmine Coluccini, Alessandra Forni, Douglas Vander A Griend, Dario PasiniAbstract:A series of homologous push–pull compounds, in which identical donor (a dimethylamino) and acceptor (a Malonate Ester) functionalities endcap crescent PPV fragments, exhibit striking differences in their supramolecular recognition of cations acting as Lewis acids. The shorter conjugated compound (one phenyl ring) coordinates a wide variety of lanthanide cations (Eu3+, Yb3+ and Er3+) in MeCN solutions to the 1,3-dicarbonyl acceptor end, resulting in an overall supramolecular polarization of the system (red shift of the intramolecular charge-transfer ICT band). With the “hard” cation Sc3+, recognition switches to the tertiary amine donor end, turning the conjugated system from D–π–A to A–π–A, and resulting in a blue shift of the ICT band upon complexation. Interestingly, increasing the conjugation by means of the insertion of sequential p-phenylenevinylene units into the ligand results in coordination to the donor end regardless of cation “hardness” (Sc3+, Eu3+ and Er3+), suggesting a relative change in the nucleophilicity of the two coordinating ends when increasing the length of the conjugated π-bridge. Such a hypothesis is supported by quantum chemical calculations on the ligands and subsequent atomic charges determination using two independent approaches (QTAIM and CHelpG). The characterization of the thermodynamic stabilities and the dimensionalities of the ligand–cation complexes in solution reveals striking differences from case to case, yet increasing affinities (from log Kav = 2.5 to log Kav = 4.9) are recorded with the increase of the π-conjugated bridge.
-
switching of emissive and nlo properties in push pull chromophores with crescent ppv like structures
Physical Chemistry Chemical Physics, 2013Co-Authors: Carmine Coluccini, Arvind K Sharma, Marco Caricato, Angelo Sironi, Elena Cariati, Stefania Righetto, Elisa Tordin, Chiara Botta, Alessandra Forni, Dario PasiniAbstract:We report on a series of novel homologous push–pull compounds, in which identical donor (a dimethylamino) and acceptor (a Malonate Ester) functionalities endcap crescent PPV fragments, bearing, respectively, 1, 2 and 3 p-phenylenevinylene units in direct linear conjugation (compounds 7–9). The three compounds exhibit striking differences in their linear and nonlinear optical properties. The shorter compound 7 exhibits aggregation-induced emission with a strong luminescence in the solid state (blue emission, photoluminescence quantum yield 38%), and it is nonemissive in solution; the more extended conjugated systems 8 and 9 show classical aggregation-caused quenching in the solid state, while high quantum yield photoluminescence (21 and 93% in toluene) is restored in diluted solutions, through mechanisms involving intramolecular charge transfer in the excited states. EFISH measurements in solutions demonstrate a strong solvent and concentration dependence. As rationalized with the aid of molecular modelling, compounds 8 and, more markedly, 9 aggregate in stable centrosymmetric dimers in solution.
Marco Caricato - One of the best experts on this subject based on the ideXlab platform.
-
from red to blue shift switching the binding affinity from the acceptor to the donor end by increasing the π bridge in push pull chromophores with coordinative ends
New Journal of Chemistry, 2013Co-Authors: Marco Caricato, Carmine Coluccini, Alessandra Forni, Douglas Vander A Griend, Dario PasiniAbstract:A series of homologous push–pull compounds, in which identical donor (a dimethylamino) and acceptor (a Malonate Ester) functionalities endcap crescent PPV fragments, exhibit striking differences in their supramolecular recognition of cations acting as Lewis acids. The shorter conjugated compound (one phenyl ring) coordinates a wide variety of lanthanide cations (Eu3+, Yb3+ and Er3+) in MeCN solutions to the 1,3-dicarbonyl acceptor end, resulting in an overall supramolecular polarization of the system (red shift of the intramolecular charge-transfer ICT band). With the “hard” cation Sc3+, recognition switches to the tertiary amine donor end, turning the conjugated system from D–π–A to A–π–A, and resulting in a blue shift of the ICT band upon complexation. Interestingly, increasing the conjugation by means of the insertion of sequential p-phenylenevinylene units into the ligand results in coordination to the donor end regardless of cation “hardness” (Sc3+, Eu3+ and Er3+), suggesting a relative change in the nucleophilicity of the two coordinating ends when increasing the length of the conjugated π-bridge. Such a hypothesis is supported by quantum chemical calculations on the ligands and subsequent atomic charges determination using two independent approaches (QTAIM and CHelpG). The characterization of the thermodynamic stabilities and the dimensionalities of the ligand–cation complexes in solution reveals striking differences from case to case, yet increasing affinities (from log Kav = 2.5 to log Kav = 4.9) are recorded with the increase of the π-conjugated bridge.
-
switching of emissive and nlo properties in push pull chromophores with crescent ppv like structures
Physical Chemistry Chemical Physics, 2013Co-Authors: Carmine Coluccini, Arvind K Sharma, Marco Caricato, Angelo Sironi, Elena Cariati, Stefania Righetto, Elisa Tordin, Chiara Botta, Alessandra Forni, Dario PasiniAbstract:We report on a series of novel homologous push–pull compounds, in which identical donor (a dimethylamino) and acceptor (a Malonate Ester) functionalities endcap crescent PPV fragments, bearing, respectively, 1, 2 and 3 p-phenylenevinylene units in direct linear conjugation (compounds 7–9). The three compounds exhibit striking differences in their linear and nonlinear optical properties. The shorter compound 7 exhibits aggregation-induced emission with a strong luminescence in the solid state (blue emission, photoluminescence quantum yield 38%), and it is nonemissive in solution; the more extended conjugated systems 8 and 9 show classical aggregation-caused quenching in the solid state, while high quantum yield photoluminescence (21 and 93% in toluene) is restored in diluted solutions, through mechanisms involving intramolecular charge transfer in the excited states. EFISH measurements in solutions demonstrate a strong solvent and concentration dependence. As rationalized with the aid of molecular modelling, compounds 8 and, more markedly, 9 aggregate in stable centrosymmetric dimers in solution.
Alessandra Forni - One of the best experts on this subject based on the ideXlab platform.
-
from red to blue shift switching the binding affinity from the acceptor to the donor end by increasing the π bridge in push pull chromophores with coordinative ends
New Journal of Chemistry, 2013Co-Authors: Marco Caricato, Carmine Coluccini, Alessandra Forni, Douglas Vander A Griend, Dario PasiniAbstract:A series of homologous push–pull compounds, in which identical donor (a dimethylamino) and acceptor (a Malonate Ester) functionalities endcap crescent PPV fragments, exhibit striking differences in their supramolecular recognition of cations acting as Lewis acids. The shorter conjugated compound (one phenyl ring) coordinates a wide variety of lanthanide cations (Eu3+, Yb3+ and Er3+) in MeCN solutions to the 1,3-dicarbonyl acceptor end, resulting in an overall supramolecular polarization of the system (red shift of the intramolecular charge-transfer ICT band). With the “hard” cation Sc3+, recognition switches to the tertiary amine donor end, turning the conjugated system from D–π–A to A–π–A, and resulting in a blue shift of the ICT band upon complexation. Interestingly, increasing the conjugation by means of the insertion of sequential p-phenylenevinylene units into the ligand results in coordination to the donor end regardless of cation “hardness” (Sc3+, Eu3+ and Er3+), suggesting a relative change in the nucleophilicity of the two coordinating ends when increasing the length of the conjugated π-bridge. Such a hypothesis is supported by quantum chemical calculations on the ligands and subsequent atomic charges determination using two independent approaches (QTAIM and CHelpG). The characterization of the thermodynamic stabilities and the dimensionalities of the ligand–cation complexes in solution reveals striking differences from case to case, yet increasing affinities (from log Kav = 2.5 to log Kav = 4.9) are recorded with the increase of the π-conjugated bridge.
-
switching of emissive and nlo properties in push pull chromophores with crescent ppv like structures
Physical Chemistry Chemical Physics, 2013Co-Authors: Carmine Coluccini, Arvind K Sharma, Marco Caricato, Angelo Sironi, Elena Cariati, Stefania Righetto, Elisa Tordin, Chiara Botta, Alessandra Forni, Dario PasiniAbstract:We report on a series of novel homologous push–pull compounds, in which identical donor (a dimethylamino) and acceptor (a Malonate Ester) functionalities endcap crescent PPV fragments, bearing, respectively, 1, 2 and 3 p-phenylenevinylene units in direct linear conjugation (compounds 7–9). The three compounds exhibit striking differences in their linear and nonlinear optical properties. The shorter compound 7 exhibits aggregation-induced emission with a strong luminescence in the solid state (blue emission, photoluminescence quantum yield 38%), and it is nonemissive in solution; the more extended conjugated systems 8 and 9 show classical aggregation-caused quenching in the solid state, while high quantum yield photoluminescence (21 and 93% in toluene) is restored in diluted solutions, through mechanisms involving intramolecular charge transfer in the excited states. EFISH measurements in solutions demonstrate a strong solvent and concentration dependence. As rationalized with the aid of molecular modelling, compounds 8 and, more markedly, 9 aggregate in stable centrosymmetric dimers in solution.
Peter S Hynes - One of the best experts on this subject based on the ideXlab platform.
-
enantioselective organocatalytic michael addition of Malonate Esters to nitro olefins using bifunctional cinchonine derivatives
Chemical Communications, 2005Co-Authors: Jinxing Ye, Darren J. Dixon, Peter S HynesAbstract:A family of 9-amino(9-deoxy) epicinchonine derivatives, possessing a range of mono- and bidentate hydrogen bond donor groups at the 9-position, were synthesised and evaluated for asymmetric organocatalytic activity in the dimethyl Malonate Michael addition to β-nitrostyrene; thiourea derivative 1e was identified as the most effective bifunctional organic catalyst and found to induce high enantioselectivity in the Malonate Ester Michael addition reaction to a range of nitro olefins.