A computational treatment of the constitutive equations of nematodynamics, based on the Leslie-Er... more A computational treatment of the constitutive equations of nematodynamics, based on the Leslie-Ericksen approach, is presented and discussed for a rotating planar nematic sample subjected to a constant magnetic field. The dynamics of the velocity v and director n fields is taken into account exactly. Coupled partial differential equations suitable to be solved numerically are worked out, in terms of derived functionals of v and n and of their spatial and time derivatives. Time-dependent patterns of the director are obtained using a finite-difference scheme in a spatial polar grid. Several experimental situations are analyzed, corresponding to common experimental setups: continuously rotating samples for different values of the rotational speed; 30 degrees and 90 degrees step-rotation experiments. A comparison is made to existing approximate treatments. Dependence upon the sample dimension is also discussed.
A numerical study of the hydrodynamics of nematic liquid crystals in cylindrical Couette geometry... more A numerical study of the hydrodynamics of nematic liquid crystals in cylindrical Couette geometry is presented, based on Leslie-Ericksen theory. The aim of this study is to interpret the director dynamics observed in Rheo-NMR experiments, where the sample (lyotropic ...
A computational treatment of Leslie-Ericksen constitutive equations of nematodynamics, is applied... more A computational treatment of Leslie-Ericksen constitutive equations of nematodynamics, is applied to an infinite planar sample, in the presence of mechanical stresses and magnetic torques. Dynamical regimes are explored in order to investigate the competing effects of magnetic and mechanical torques and backflow effects resulting from coupling of velocity and director fields and to understand the transient behaviour of the
Computationally exact and approximate solutions of the Leslie-Ericksen equations for nematic liqu... more Computationally exact and approximate solutions of the Leslie-Ericksen equations for nematic liquid crystals in two dimensions are employed to calculate director distributions in cylindrical samples, rotating under the influence of a magnetic field. In particular, the time evolution of systems prepared initially in metastable states with respect to the magnetic field is investigated, and calculated director distributions are used to interpret rheo-NMR experiments in nematic liquid crystal polymers.
... K2yord.c: nematic liquid crystals; Leslie-Ericksen equations; rheology; hydrodynamics Introdu... more ... K2yord.c: nematic liquid crystals; Leslie-Ericksen equations; rheology; hydrodynamics Introduction by Professor David Dunrnur? ... Corresponding author: A.Polimeno@chfi.unipd.it i. Department of Chemistry, University of Southampton, United Kingdom 135 Page 2. ...
A computational treatment of Leslie-Ericksen constitutive equations of nematodynamics, is applied... more A computational treatment of Leslie-Ericksen constitutive equations of nematodynamics, is applied to an infinite planar sample, in the presence of mechanical stresses and magnetic torques. Dynamical regimes are explored in order to investigate the competing effects of magnetic and mechanical torques and backflow effects resulting from coupling of velocity and director fields and to understand the transient behaviour of the
A computational treatment of the constitutive equations of nematodynamics, based on the Leslie-Er... more A computational treatment of the constitutive equations of nematodynamics, based on the Leslie-Ericksen approach, is presented and discussed for a rotating planar nematic sample subjected to a constant magnetic field. The dynamics of the velocity v and director n fields is taken into account exactly. Coupled partial differential equations suitable to be solved numerically are worked out, in terms of derived functionals of v and n and of their spatial and time derivatives. Time-dependent patterns of the director are obtained using a finite-difference scheme in a spatial polar grid. Several experimental situations are analyzed, corresponding to common experimental setups: continuously rotating samples for different values of the rotational speed; 30 degrees and 90 degrees step-rotation experiments. A comparison is made to existing approximate treatments. Dependence upon the sample dimension is also discussed.
... Laura Orian,* † Joost NP van Stralen, ‡ and F. Matthias Bickelhaupt* ‡. ... 2. While the fund... more ... Laura Orian,* † Joost NP van Stralen, ‡ and F. Matthias Bickelhaupt* ‡. ... 2. While the fundamental research of Wakatsuki and Yamazaki, 3 Bönnemann, 4 and Vollhardt 5 established that cobalt-based catalysts are the compounds of primary choice for the [2+2+2] cyclizations ...
ABSTRACT A systematic analysis of the linkage isomerism of nitriles in half'sandwichfive-... more ABSTRACT A systematic analysis of the linkage isomerism of nitriles in half'sandwichfive-membered rhodacycles is presented for 15 nitriles of the general formula RCN. The hitherto elusive transition states connecting the two isomers have been located using advanced DFT methods.
A series of heterobimetallic complexes of general structure [RhL2{η5-(2-ferrocenyl)indenyl}] (L2=... more A series of heterobimetallic complexes of general structure [RhL2{η5-(2-ferrocenyl)indenyl}] (L2=cod, nbd, L=CO; cod=cyclooctadiene; nbd=norbornadiene) has been synthesised with the aim of tuning the metal–metal interaction in their mixed-valence ions generated both by chemical and electrochemical oxidation, and the results are compared with those obtained for [RhL2{η5-(1-ferrocenyl)indenyl}] isomers. Crystallographic studies and DFT calculations provide a detailed description of the structural and electronic features of these complexes evidencing a significant difference in the extent of planarity of the flexible bridging ligand between the 1- and 2-ferrocenyl isomers. Independent experimental probes, in particular the potential splitting in the cyclic voltammograms and the IT bands in the near-IR spectra, are rationalised in the framework of Marcus–Hush theory and at quantum chemistry level by DFT and TD-DFT methods. These methods allow us to establish a trend based on the magnitude of iron–rhodium electronic coupling Hab ranging from valence trapped to almost delocalised ions. The quasi planar bridge and the olefin ancillary ligands make [Rh(nbd){η5-(2-ferrocenyl)indenyl}]+ and [Rh(cod){η5-(2-ferrocenyl)indenyl}]+ rare examples of heterobimetallic systems which can be classified as borderline Class II/Class III species.
A series of heterobimetallic η6-[(ferrocenyl)indene]-Cr(CO)3 complexes differing for the position... more A series of heterobimetallic η6-[(ferrocenyl)indene]-Cr(CO)3 complexes differing for the position of the ferrocenyl group, 1-(ferrocenyl)indene and 2-(ferrocenyl)indene, and the degree of indene methylation (tetramethyl- and hexamethyl-) have been prepared and studied with the aim to stabilise the mono- and dications generated by chemical and electrochemical oxidation, and at same time to tune the metal–metal electronic coupling in the mixed-valence cations.
... Saverio Santi,* Laura Orian, Alessandro Donoli, Christian Durante, Annalisa Bisello, Paolo Ga... more ... Saverio Santi,* Laura Orian, Alessandro Donoli, Christian Durante, Annalisa Bisello, Paolo Ganis, and Alberto Ceccon*. Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy. Laura Crociani and Franco Benetollo. ...
ABSTRACT A series of ferrocenyl-based complexes of general structure [η5-(2-ferrocenyl)indenyl]ML... more ABSTRACT A series of ferrocenyl-based complexes of general structure [η5-(2-ferrocenyl)indenyl]MLn [MLn = RuCp*, FeCp, IrCOD, Mn(CO)3, and Cr(CO)2NO] were synthesized with the aim of tuning the effect of the nature of the second metal group MLn on the magnitude of the metal−metal electronic coupling in their mixed valence ions generated by electrochemical oxidation. The electronic interaction was probed by determining different and independent physical properties, the potential splitting in the cyclic voltammograms, and the IT bands in the near-IR spectra, which were rationalized in the framework of Marcus−Hush theory and at the quantum chemistry level by the density functional theory and TD density functional theory methods. On the basis of the obtained results, we were able to establish a trend based on the magnitude of the Fe−M electron transfer parameters Hab and α ranging from weakly to moderately coupled mixed valence ions.
A computational treatment of the constitutive equations of nematodynamics, based on the Leslie-Er... more A computational treatment of the constitutive equations of nematodynamics, based on the Leslie-Ericksen approach, is presented and discussed for a rotating planar nematic sample subjected to a constant magnetic field. The dynamics of the velocity v and director n fields is taken into account exactly. Coupled partial differential equations suitable to be solved numerically are worked out, in terms of derived functionals of v and n and of their spatial and time derivatives. Time-dependent patterns of the director are obtained using a finite-difference scheme in a spatial polar grid. Several experimental situations are analyzed, corresponding to common experimental setups: continuously rotating samples for different values of the rotational speed; 30 degrees and 90 degrees step-rotation experiments. A comparison is made to existing approximate treatments. Dependence upon the sample dimension is also discussed.
A numerical study of the hydrodynamics of nematic liquid crystals in cylindrical Couette geometry... more A numerical study of the hydrodynamics of nematic liquid crystals in cylindrical Couette geometry is presented, based on Leslie-Ericksen theory. The aim of this study is to interpret the director dynamics observed in Rheo-NMR experiments, where the sample (lyotropic ...
A computational treatment of Leslie-Ericksen constitutive equations of nematodynamics, is applied... more A computational treatment of Leslie-Ericksen constitutive equations of nematodynamics, is applied to an infinite planar sample, in the presence of mechanical stresses and magnetic torques. Dynamical regimes are explored in order to investigate the competing effects of magnetic and mechanical torques and backflow effects resulting from coupling of velocity and director fields and to understand the transient behaviour of the
Computationally exact and approximate solutions of the Leslie-Ericksen equations for nematic liqu... more Computationally exact and approximate solutions of the Leslie-Ericksen equations for nematic liquid crystals in two dimensions are employed to calculate director distributions in cylindrical samples, rotating under the influence of a magnetic field. In particular, the time evolution of systems prepared initially in metastable states with respect to the magnetic field is investigated, and calculated director distributions are used to interpret rheo-NMR experiments in nematic liquid crystal polymers.
... K2yord.c: nematic liquid crystals; Leslie-Ericksen equations; rheology; hydrodynamics Introdu... more ... K2yord.c: nematic liquid crystals; Leslie-Ericksen equations; rheology; hydrodynamics Introduction by Professor David Dunrnur? ... Corresponding author: A.Polimeno@chfi.unipd.it i. Department of Chemistry, University of Southampton, United Kingdom 135 Page 2. ...
A computational treatment of Leslie-Ericksen constitutive equations of nematodynamics, is applied... more A computational treatment of Leslie-Ericksen constitutive equations of nematodynamics, is applied to an infinite planar sample, in the presence of mechanical stresses and magnetic torques. Dynamical regimes are explored in order to investigate the competing effects of magnetic and mechanical torques and backflow effects resulting from coupling of velocity and director fields and to understand the transient behaviour of the
A computational treatment of the constitutive equations of nematodynamics, based on the Leslie-Er... more A computational treatment of the constitutive equations of nematodynamics, based on the Leslie-Ericksen approach, is presented and discussed for a rotating planar nematic sample subjected to a constant magnetic field. The dynamics of the velocity v and director n fields is taken into account exactly. Coupled partial differential equations suitable to be solved numerically are worked out, in terms of derived functionals of v and n and of their spatial and time derivatives. Time-dependent patterns of the director are obtained using a finite-difference scheme in a spatial polar grid. Several experimental situations are analyzed, corresponding to common experimental setups: continuously rotating samples for different values of the rotational speed; 30 degrees and 90 degrees step-rotation experiments. A comparison is made to existing approximate treatments. Dependence upon the sample dimension is also discussed.
... Laura Orian,* † Joost NP van Stralen, ‡ and F. Matthias Bickelhaupt* ‡. ... 2. While the fund... more ... Laura Orian,* † Joost NP van Stralen, ‡ and F. Matthias Bickelhaupt* ‡. ... 2. While the fundamental research of Wakatsuki and Yamazaki, 3 Bönnemann, 4 and Vollhardt 5 established that cobalt-based catalysts are the compounds of primary choice for the [2+2+2] cyclizations ...
ABSTRACT A systematic analysis of the linkage isomerism of nitriles in half'sandwichfive-... more ABSTRACT A systematic analysis of the linkage isomerism of nitriles in half'sandwichfive-membered rhodacycles is presented for 15 nitriles of the general formula RCN. The hitherto elusive transition states connecting the two isomers have been located using advanced DFT methods.
A series of heterobimetallic complexes of general structure [RhL2{η5-(2-ferrocenyl)indenyl}] (L2=... more A series of heterobimetallic complexes of general structure [RhL2{η5-(2-ferrocenyl)indenyl}] (L2=cod, nbd, L=CO; cod=cyclooctadiene; nbd=norbornadiene) has been synthesised with the aim of tuning the metal–metal interaction in their mixed-valence ions generated both by chemical and electrochemical oxidation, and the results are compared with those obtained for [RhL2{η5-(1-ferrocenyl)indenyl}] isomers. Crystallographic studies and DFT calculations provide a detailed description of the structural and electronic features of these complexes evidencing a significant difference in the extent of planarity of the flexible bridging ligand between the 1- and 2-ferrocenyl isomers. Independent experimental probes, in particular the potential splitting in the cyclic voltammograms and the IT bands in the near-IR spectra, are rationalised in the framework of Marcus–Hush theory and at quantum chemistry level by DFT and TD-DFT methods. These methods allow us to establish a trend based on the magnitude of iron–rhodium electronic coupling Hab ranging from valence trapped to almost delocalised ions. The quasi planar bridge and the olefin ancillary ligands make [Rh(nbd){η5-(2-ferrocenyl)indenyl}]+ and [Rh(cod){η5-(2-ferrocenyl)indenyl}]+ rare examples of heterobimetallic systems which can be classified as borderline Class II/Class III species.
A series of heterobimetallic η6-[(ferrocenyl)indene]-Cr(CO)3 complexes differing for the position... more A series of heterobimetallic η6-[(ferrocenyl)indene]-Cr(CO)3 complexes differing for the position of the ferrocenyl group, 1-(ferrocenyl)indene and 2-(ferrocenyl)indene, and the degree of indene methylation (tetramethyl- and hexamethyl-) have been prepared and studied with the aim to stabilise the mono- and dications generated by chemical and electrochemical oxidation, and at same time to tune the metal–metal electronic coupling in the mixed-valence cations.
... Saverio Santi,* Laura Orian, Alessandro Donoli, Christian Durante, Annalisa Bisello, Paolo Ga... more ... Saverio Santi,* Laura Orian, Alessandro Donoli, Christian Durante, Annalisa Bisello, Paolo Ganis, and Alberto Ceccon*. Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy. Laura Crociani and Franco Benetollo. ...
ABSTRACT A series of ferrocenyl-based complexes of general structure [η5-(2-ferrocenyl)indenyl]ML... more ABSTRACT A series of ferrocenyl-based complexes of general structure [η5-(2-ferrocenyl)indenyl]MLn [MLn = RuCp*, FeCp, IrCOD, Mn(CO)3, and Cr(CO)2NO] were synthesized with the aim of tuning the effect of the nature of the second metal group MLn on the magnitude of the metal−metal electronic coupling in their mixed valence ions generated by electrochemical oxidation. The electronic interaction was probed by determining different and independent physical properties, the potential splitting in the cyclic voltammograms, and the IT bands in the near-IR spectra, which were rationalized in the framework of Marcus−Hush theory and at the quantum chemistry level by the density functional theory and TD density functional theory methods. On the basis of the obtained results, we were able to establish a trend based on the magnitude of the Fe−M electron transfer parameters Hab and α ranging from weakly to moderately coupled mixed valence ions.
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