Hybridization in 1,5,9-Tridehydro(l2)Annulene

The hybridization \u27in l,5,9-tridehydro(12)annulene has been calculated by the method of maximum overlap. The results show that the hybrids describing CC double bonds and CC triple bonds have more s-character than the hybrids of the same carbon atoms involved in single CC bonds. Consequently, CC double and CC triple bonds are strengthened not only by the additional n-type overlap, but also by an increase of cr-type overlap, which accompanies the rise of the s-content. By using available empirical correlations a comparison between calculated and experimental NMR data (spin-spin coupling constant J (C13- H) and chemical shift i;) is made

Vibrational Spectra and Force Constants of Bicyclic Molecules. I. Norbornane and Norbornane-d4

Norbornan.e (bicyclo[2.2.l]heptane) and its derivatives have been extensively studied by chemical and physical methods. Since norbornane represents an important strained molecule, particular attention was payed tci its geometry1 and bonding properties2• However, no vibrational analysis of norbornane or its derivatives has been undertaiken. Only partly analysed vibrational spectra are reported3• Therefore we find des~rable to undertake a complete vibrational analysis of norbornane and its deuterated species

Magnetoelectrics and multiferroics: theory, synthesis, characterisation, preliminary results and perspectives for all-optical manipulations

Solid state compounds exhibiting multiple and coupled macroscopic orders, named multiferroics, represent a challenge for both theoretical and experimental modern condensed-matter physics. Spins and the electric polarisation in conventional magnetic and ferroelectric materials can be manipulated on their fundamental timescales, by means of femtosecond laser pulses. In view of the resounding success and popularity of the all-optical approach, it is only natural to wonder about the application of this scheme to study the intrinsic coupling between spins and charges in multiferroics. Deeply fundamental questions arise: can ultrashort laser pulses deterministically activate, enhance or suppress the magnetoelectric coupling on the femtosecond timescale? Can these processes be triggered in a fully coherent fashion, thus being unrestrained by any thermal load? Which mechanism of spin-charge coupling is most favourable to overcome these overarching and daunting challenges? This problem is interdisciplinary in nature, requiring contributions from materials science and condensed matter physics from both theoretical and experimental perspectives. High-quality materials suitable for optical investigations have to be identified, synthetized and characterised. General and valid models offer then a guide to the plethora of possible light-induced processes, resulting in the desired ultrafast multiferroic manipulations. Finally, healthy experimental schemes, able to unambiguously track the ultrafast dynamics of either the ferroelectric or the magnetic order parameter have to be developed and implemented. Our motivation to write this review is to lay a broad and multidisciplinary foundation, which may be employed as a starting point for non-equilibrium approaches to the manipulation of the multiferroicity on the femtosecond timescale. This was also one of the main goals of the COST Action MAGNETOFON, whose network constitutes the core of the authors of this review. The present work thus represents a part of the scientific legacy of MAGNETOFON itself

A detailed experimental and computational study of monocarbohydrazones

The substituent and solvent effect on intramolecular charge transfer (ICT) of twelve monocarbohydrazones (mCHs) were studied using experimental and theoretical methodology. The effects of specific and non-specific solvent-solute interactions on the UV-Vis absorption maxima shifts were evaluated using linear free energy relationships (LFERs) principles, i.e. using the Kamlet-Taft and Catalan models. Linear free energy relationships in the form of single substituent parameter equation (SSP) was used to analyze substituent effect on UV-Vis, NMR and pK(a) change. According to crystallographic data and quantum chemical calculations, the trans (E) form was found to be more stable. A photochromism of compounds with 2-hydroxyphenyl and 2-pyridylimino groups substituted at imine carbon atom results in E/Z isomerization due to creation of intermolecular hydrogen bond in E and Z form, respectively. Multiple stage mass spectrometry (MS-MSn) analysis was applied to define main fragmentation pathways. Furthermore, the experimental findings were interpreted with the aid of ab initio MP2/6-311 G(d,p) and time-dependent density functional (TD-DFT) methods. TD-DFT calculations were performed to quantify the efficiency of intramolecular charge transfer (ICT) with the aid of the charge-transfer distance (DCT) and the amount of transferred charge (QCT) calculation. It was found that both substituents and solvents influence electron density shift i.e. extent of conjugation, and affect ICT character in the course of excitation