Iñaki Silanes - Academia.edu (original) (raw)
Papers by Iñaki Silanes
Physical Review E, 2002
The relative stability of various charge states of a number of selected elements has been studied... more The relative stability of various charge states of a number of selected elements has been studied as a function of increasing screening due to a weakly bound plasma represented by the statically screened Coulomb potential of the Yukawa-type. Elements with positive electron affinity in a vacuum are predicted to undergo a sequential electron detachment process from anionic state to the cationic one as the inverse screening length of plasma increases. Conversely, elements with negative electron affinity in a vacuum present only two charge states, neutral and positive. At small screening the neutral is the most stable charge state, and as the screening increases the cation develops as the most stable charge state. Values of the inverse screening length for each of the transitions have been calculated and discussed.
Organometallics, 2006
In this paper we make use of a carefully chosen counterion model, B(CF 2 Cl) 3 , for a molecularl... more In this paper we make use of a carefully chosen counterion model, B(CF 2 Cl) 3 , for a molecularly welldefined metallocenic catalyst counterion, B(C 6 F 5 ) 3 , to perform a comparison of Cp 2 M(CH 3 ) 2 -type metallocene activities toward ethylene polymerization, for M ) Ti, Zr, and Hf. Monomer complexation and chain-insertion barriers are calculated and discussed, and a higher intrinsic activity for titanium is derived. Calculations are also performed in order to add further evidence of the suitability of the counterion model used. We conclude that the model employed here can act as an accurate enough substitute for the original borate in quantum mechanical calculations.
Nano Letters, 2009
The confinement of surface-state electrons by a complex supramolecular network is studied using l... more The confinement of surface-state electrons by a complex supramolecular network is studied using low-temperature scanning tunneling microscopy and rationalized by electronic structure calculations using a boundary element method. We focus on the self-assembly of dicarbonitrilesexiphenyl molecules on Ag(111) creating an open kagomé topology tessellating the surface into pores with different size and symmetry. This superlattice imposes a distinct surface electronic structure modulation, as observed by tunneling spectroscopy and thus acts as a dichotomous array of quantum corrals. The inhomogenous lateral electronic density distribution in the chiral cavities is reproduced by an effective pseudopotential model. Our results demonstrate the engineering of ensembles of elaborate quantum resonance states by molecular selfassembly at surfaces.
Journal of the American Chemical Society, 2005
A systematic study of cation-pi interactions between alkali metal ions and the cyclopentadienyl r... more A systematic study of cation-pi interactions between alkali metal ions and the cyclopentadienyl ring of ferrocene is presented. The alkali metal (Li+, Na+, K+, Rb+, Cs+) salts of the ditopic mono(pyrazol-1-yl)borate ligand [1,1'-fc(BMe2pz)2]2- crystallize from dimethoxyethane as multiple-decker sandwich complexes with the M+ ions bound to the pi faces of the ferrocene cyclopentadienyl rings in an eta5 manner (fc = (C5H4)2Fe; pz = pyrazolyl). X-ray crystallography of the lithium complex reveals discrete trimetallic entities with each lithium ion being coordinated by only one cyclopentadienyl ring. The sodium salt forms polyanionic zigzag chains where each Na+ ion bridges the cyclopentadienyl rings of two ferrocene moieties. Linear columns [-CpR-Fe-CpR-M+-CpR-Fe-CpR-M+-](infinity) (R = [-BMe2pz]-) are established by the K+, Rb+, and Cs+ derivatives in the solid state. According to DFT calculations, the binding enthalpies of M+-eta5(ferrocene) model complexes are about 20% higher as compared to the corresponding M+-eta6(benzene) aggregates when M+ = Li+ or Na+. For K+ and Rb+, the degree of cation-pi interaction with both aromatics is about the same. The binding sequence along the M+-eta5(ferrocene) series follows a classical electrostatic trend with the smaller ions being more tightly bound.
Journal of the American Chemical Society, 2001
The stable isomers of the ferrocene--lithium cation gas-phase ion complex have been studied with ... more The stable isomers of the ferrocene--lithium cation gas-phase ion complex have been studied with the hybrid density functional theory. The method of calculation chosen has been tested checking its performance for the more studied protonated ferrocene species. Our calculations demonstrate that the procedure used is reliable. We have found two isomers of the ferrocene--lithium cation complex separated by a barrier of 25.6 kcal/mol. The most stable isomer of this complex has Li(+) on-top of one of the cyclopentadienyls, while in the least stable isomer Li(+) binds the central iron metal. The latter isomer has been characterized as a planetary system in the sense that Li(+) has one thermally accessible planar orbit around the central ferrocene moiety. Our calculations lead to a value of ferrocene's gas-phase lithium cation basicity of 37.4 kcal/mol for the on-top complex and 29.4 kcal/mol for the metal-bound complex.
Advanced Functional Materials, 2009
Physical Review E, 2002
The relative stability of various charge states of a number of selected elements has been studied... more The relative stability of various charge states of a number of selected elements has been studied as a function of increasing screening due to a weakly bound plasma represented by the statically screened Coulomb potential of the Yukawa-type. Elements with positive electron affinity in a vacuum are predicted to undergo a sequential electron detachment process from anionic state to the cationic one as the inverse screening length of plasma increases. Conversely, elements with negative electron affinity in a vacuum present only two charge states, neutral and positive. At small screening the neutral is the most stable charge state, and as the screening increases the cation develops as the most stable charge state. Values of the inverse screening length for each of the transitions have been calculated and discussed.
Organometallics, 2006
In this paper we make use of a carefully chosen counterion model, B(CF 2 Cl) 3 , for a molecularl... more In this paper we make use of a carefully chosen counterion model, B(CF 2 Cl) 3 , for a molecularly welldefined metallocenic catalyst counterion, B(C 6 F 5 ) 3 , to perform a comparison of Cp 2 M(CH 3 ) 2 -type metallocene activities toward ethylene polymerization, for M ) Ti, Zr, and Hf. Monomer complexation and chain-insertion barriers are calculated and discussed, and a higher intrinsic activity for titanium is derived. Calculations are also performed in order to add further evidence of the suitability of the counterion model used. We conclude that the model employed here can act as an accurate enough substitute for the original borate in quantum mechanical calculations.
Nano Letters, 2009
The confinement of surface-state electrons by a complex supramolecular network is studied using l... more The confinement of surface-state electrons by a complex supramolecular network is studied using low-temperature scanning tunneling microscopy and rationalized by electronic structure calculations using a boundary element method. We focus on the self-assembly of dicarbonitrilesexiphenyl molecules on Ag(111) creating an open kagomé topology tessellating the surface into pores with different size and symmetry. This superlattice imposes a distinct surface electronic structure modulation, as observed by tunneling spectroscopy and thus acts as a dichotomous array of quantum corrals. The inhomogenous lateral electronic density distribution in the chiral cavities is reproduced by an effective pseudopotential model. Our results demonstrate the engineering of ensembles of elaborate quantum resonance states by molecular selfassembly at surfaces.
Journal of the American Chemical Society, 2005
A systematic study of cation-pi interactions between alkali metal ions and the cyclopentadienyl r... more A systematic study of cation-pi interactions between alkali metal ions and the cyclopentadienyl ring of ferrocene is presented. The alkali metal (Li+, Na+, K+, Rb+, Cs+) salts of the ditopic mono(pyrazol-1-yl)borate ligand [1,1'-fc(BMe2pz)2]2- crystallize from dimethoxyethane as multiple-decker sandwich complexes with the M+ ions bound to the pi faces of the ferrocene cyclopentadienyl rings in an eta5 manner (fc = (C5H4)2Fe; pz = pyrazolyl). X-ray crystallography of the lithium complex reveals discrete trimetallic entities with each lithium ion being coordinated by only one cyclopentadienyl ring. The sodium salt forms polyanionic zigzag chains where each Na+ ion bridges the cyclopentadienyl rings of two ferrocene moieties. Linear columns [-CpR-Fe-CpR-M+-CpR-Fe-CpR-M+-](infinity) (R = [-BMe2pz]-) are established by the K+, Rb+, and Cs+ derivatives in the solid state. According to DFT calculations, the binding enthalpies of M+-eta5(ferrocene) model complexes are about 20% higher as compared to the corresponding M+-eta6(benzene) aggregates when M+ = Li+ or Na+. For K+ and Rb+, the degree of cation-pi interaction with both aromatics is about the same. The binding sequence along the M+-eta5(ferrocene) series follows a classical electrostatic trend with the smaller ions being more tightly bound.
Journal of the American Chemical Society, 2001
The stable isomers of the ferrocene--lithium cation gas-phase ion complex have been studied with ... more The stable isomers of the ferrocene--lithium cation gas-phase ion complex have been studied with the hybrid density functional theory. The method of calculation chosen has been tested checking its performance for the more studied protonated ferrocene species. Our calculations demonstrate that the procedure used is reliable. We have found two isomers of the ferrocene--lithium cation complex separated by a barrier of 25.6 kcal/mol. The most stable isomer of this complex has Li(+) on-top of one of the cyclopentadienyls, while in the least stable isomer Li(+) binds the central iron metal. The latter isomer has been characterized as a planetary system in the sense that Li(+) has one thermally accessible planar orbit around the central ferrocene moiety. Our calculations lead to a value of ferrocene's gas-phase lithium cation basicity of 37.4 kcal/mol for the on-top complex and 29.4 kcal/mol for the metal-bound complex.
Advanced Functional Materials, 2009