Search results for "Intramolecular force"

Halogen⋯halogen interactions in the self-assembly of one-dimensional 2,2′-bipyrimidine-based CuIIReIV systems

2018

Two one-dimensional CuIIReIV coordination polymers of the general formula {[ReIVCl4(μ-bpym)CuIIX2]·solvent}n [where bpym = 2,2′-bipyrimidine, X = Cl (1) and Br (2), and solvent = H2O (1) and CHCl3 (2)] have been prepared and characterised structurally and magnetically. Both compounds crystallise in the monoclinic system with space groups P21/c (1) and P21/n (2). Each CuII ion is bonded to two cis nitrogen atoms from the bpym ligand and to four halogen atoms. Two of these halogen atoms are placed in the equatorial plane and the other two are filling the axial positions of the CuII ion, thus generating a distorted octahedral environment for this metal ion in 1 and 2. In both compounds, the Re…

Hybrid Particle-Field Molecular Dynamics Simulations of Charged Amphiphiles in an Aqueous Environment.

2018

We develop and test specific coarse-grained models for charged amphiphilic systems such as palmitoyloleoylphosphatidylglycerol (POPG) lipid bilayer and sodium dodecyl sulfate (SDS) surfactant in an aqueous environment, to verify the ability of the hybrid particle-field method to provide a realistic description of polyelectrolytes. According to the hybrid approach, the intramolecular interactions are treated by a standard molecular Hamiltonian, and the nonelectrostatic intermolecular forces are described by density fields. Electrostatics is introduced as an additional external field obtained by a modified particle-mesh Ewald procedure, as recently proposed [Zhu et al. Phys. Chem. Chem. Phys.…

Modeling the Interaction of Carbon Monoxide with Flexible Graphene: From Coupled Cluster Calculations to Molecular-Dynamics Simulations

2018

The interaction of CO with graphene was studied at different theoretical levels. Quantum-mechanical calculations on finite graphene models with the use of coronene for coupled cluster calculations and circumcoronene for B97D calculations showed that there was no preferential site for adsorption and that the most important factor was the orientation of CO relative to graphene. The parallel orientation was preferred, with binding energies around 9 kJ mol-1 at the CCSD(T) and B97D levels, which was in good agreement with experimental findings. From a large number of CO-circumcoronene and CO-CO interactions, computed at different distances and randomly generated orientations, parameters were fi…

Complexes of an anionic poly(p-phenylene) polyelectrolyte and dioctadecylammonium bromide at the air–water interface

1999

Abstract By spreading dioctadecyldimethylammonium bromide on a subphase containing rigid rod-like anionic poly( p -phenylene) sulfonate, a complex monolayer is formed in situ at the air–water interface. Complexation results in an increase of the area per amphiphile molecule compared to the amphiphile on pure water. The change in structural order upon complexation and subsequent compression of the monolayer can be demonstrated employing UV/Vis spectroscopy: A red-shift of the polymer absorption band upon compression and a subsequent partial reversion of this shift after monolayer collapse can be observed. The peak shift is discussed to be a result of the electronic interaction of the π -syst…

2016

Two light-emitting polyphenylene dendrimers with both hole and electron transporting moieties were synthesized and characterized. Both molecules exhibited pure blue emission solely from the pyrene core and efficient surface-to-core energy transfers when characterized in a nonpolar environment. In particular, the carbazole- and oxadiazole-functionalized dendrimer (D1) manifested a pure blue emission from the pyrene core without showing intramolecular charge transfer (ICT) in environments with increasing polarity. On the other hand, the triphenylamine- and oxadiazole-functionalized one (D2) displayed notable ICT with dual emission from both the core and an ICT state in highly polar solvents. …

Double D–π–A branched dyes – a new class of metal-free organic dyes for efficient dye-sensitized solar cells

2017

Double branched donor acceptor compounds (D–π–A)2L, whose separate branches are linked by saturated chains or ring systems, are highly promising sensitizers for dye-sensitized solar cells (DSSCs). Their photovoltaic performance η (power conversion efficiency PCE) is higher than the η value of the corresponding single branched sensitizers D–π–A. This advantage can be attributed to the lower aggregation tendency and to the higher loading density of the chromophores on the semi-conductor surface (TiO2). Moreover, the intramolecular transfer of the excitation energy can enhance the contact time of the adsorbed dye molecules in the excited state S1 and thus reduce the unwanted charge recombinati…

Synthesis, properties and charge transfer complexes of covalently attached [60]fullerene-tetrathiafulvalenes

1997

Abstract The synthesis of several fulleropyrrolidines bearing differently substitued tetrathiafulvalenes is reported. The synthetic approach used allows the introduction of ethylene spacers between the TTF and the C 60 core. Charge transfer complexes obtained from these [60]fullerene-TTF systems by reaction with tetrafluoro-tetracyano-p-quinodimethane (TCNQF 4 ) show a semiconducting behaviour; theoretical calculations predict an intramolecular CT band from the TTF moiety to the C 60 core.

Molecular flattening effect to enhance the conductivity of fused porphyrin tape thin films.

2019

The straightforward synthesis of directly fused porphyrins (porphyrin tapes) from 5,15-diphenyl porphyrinato nickel(II) complexes with different substituents on the phenyl rings is achieved while processing from the gas phase. The porphyrin tapes, exhibiting NIR absorption, are readily obtained in thin film form. The gas phase approach cuts the need for solubilizing groups allowing for the first time the study of their conductivity according to the substituent. 2-Point probe and conductivity AFM measurements evidence that reducing the size of the meso substituents, phenyl < mesityl < di(3,5-tert-butyl)phenyl < di(2,6-dodecyloxy)phenyl, improves the thin film conductivity by several orders o…

Columnar phases from semi-discoid molecules. Phase induction via hydrogen bonding and charge transfer interactions

1991

Abstract To investigate the non-linear optical properties of nitrophenylhydrazones, a series of 4-nitro- and 2,4-dinitrophenylhydrazones of substituted aromatic aldehydes were synthesized. It was found that many of the dinitrophenythydrazone derivatives are liquid-crystalline and X-ray investigations show that the mesophase corresponds to a hexagonal columnar structure. To explain this unusual behaviour it is necessary to assume that a mesogenic structure is formed by intramolecular hydrogen bonding of the dinitrophenylhydrazones. Charge transfer induced antiparallel alignment of these moleculer dipoles leads to discoid structures, forming the columnar phases.

Time-Resolved Fourier-Transform Infrared Spectroscopy on the Inter- and Intramolecular Orientational Dynamics in Ferroelectric Liquid Crystalline Dim…

1997

On a base of time-resolved step-scan IR-spectroscopy data, we present a detailed model of the segmental reorientation during the ferroelectric and electroclinic switching of a chiral liquid crystalline dimer. We detected that the magnitude of the motion of the molecular segments differ from each other: The tilt angle is maximal for the mesogens and minimal for the ``virtual polysiloxane backbone.'' In contrast to a recently published conjecture, we prove that in the \ensuremath{\mu}s scale the responses of different molecular segments are unambiguously synchronous with each other.