Synthesis of double hydrophilic poly(ethylene oxide)‐b‐poly(2‐hydroxyethyl acrylate) by single‐electron transfer–living radical polymerization

In this study, the polymerization of (2‐hydroxyethyl) acrylate (HEA), in polar media, using Cu(0)‐mediated radical polymerization also called single‐electron transfer–living radical polymerization (SET‐LRP) is reported. The kinetics aspects of both the homopolymerization and the copolymerization from a poly(ethylene oxide) (PEO) macroinitiator were analyzed by ¹H NMR. The effects of both the ligand and the solvent were studied. The polymerization was shown to reach very high monomer conversions and to proceed in a well‐controlled fashion in the presence of tris[2‐(dimethylamino)ethyl]amine Me6‐TREN and N, N,N′, N″, N″‐pentamethyldiethylenetriamine (PMDETA) in dimethylsulfoxide (DMSO). SET‐LRP of HEA was also led in water, and it was shown to be faster than in DMSO. In pure water, Me₆‐TREN allowed a better control over the molar masses and polydispersity indices than PMDETA and TREN. Double hydrophilic PEO‐b‐PHEA block copolymers, exhibiting various PHEA block lengths up to 100 HEA units, were synthesized, in the same manner, from a bromide‐terminated PEO macroinitiator. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Ultrafast Deactivation Mechanism of the Excited Singlet in the Light‐Induced Spin Crossover of [Fe(2,2′‐bipyridine)3]2+

The mechanism of the light‐induced spin crossover of the [Fe(bpy)₃]²⁺ complex (bpy=2,2′‐bipyridine) has been studied by combining accurate electronic‐structure calculations and time‐dependent approaches to calculate intersystem‐crossing rates. We investigate how the initially excited metal‐to‐ligand charge transfer (MLCT) singlet state deactivates to the final metastable high‐spin state. Although ultrafast X‐ray free‐electron spectroscopy has established that the total timescale of this process is on the order of a few tenths of a picosecond, the details of the mechanisms still remain unclear. We determine all the intermediate electronic states along the pathway from low spin to high spin and give estimates for the deactivation times of the different stages. The calculations result in a total deactivation time on the same order of magnitude as the experimentally determined rate and indicate that the complex can reach the final high‐spin state by means of different deactivation channels. The optically populated excited singlet state rapidly decays to a triplet state with an Fe d⁶(${{\rm t}{{5\hfill \atop {\rm 2g}\hfill}}}$ ${{\rm e}{{1\hfill \atop {\rm g}\hfill}}}$ ) configuration either directly or by means of a triplet MLCT state. This triplet ligand‐field state could in principle decay directly to the final quintet state, but a much faster channel is provided by internal conversion to a lower‐lying triplet state and subsequent intersystem crossing to the high‐spin state. The deactivation rate to the low‐spin ground state is much smaller, which is in line with the large quantum yield reported for the process.     

Synthesis and characterization of 2CuCN·DMSO and [CuII(DMSO)6][CuI 6(CN)8] 3-D framework compounds

Two novel complexes of CuCN were characterized by using a single-crystal X-ray diffraction technique and Raman spectroscopy. In the structure of 2CuCN·DMSO ligand molecule demonstrates unique bridging mode, being bound to two Cu^I centers via oxygen and sulfur atoms. The bridging role of both CN groups and DMSO molecules results in the formation of (CuCN·DMSO)_n framework. Along the channels of the network are running infinite zig-zag (CuCN)_n chains, which are bound to the framework by elongated Cu…(CN) bonds. A mixed-valence [Cu^II(DMSO)₆][Cu^I ₆(CN)₈] compound is composed of 3-D [Cu^I ₆(CN)₈]_n anionic framework and located in the channels of partially disordered [Cu^II(DMSO)₆]²⁺ cations.     

Approach to 5-substituted 6,7,8,9-tetrahydro-5H-pyrido[3,2-c]azepines

An approach to 5-substituted 6,7,8,9-tetrahydro-5H-pyrido[3,2-c]azepines via the cyclization of 1-(2-(3-azidopropyl)pyridin-3-yl)alkanones under Staudinger–aza-Wittig reaction conditions is described. The overall reaction sequence includes eight steps and allows for the preparation of gram quantities of the title products. In some cases, the formation of 5,7,8,9-tetrahydrooxepino[4,3-b]pyridine derivatives was observed.     

Electronic structure and solvatochromism of merocyanines NMR spectroscopic point of view

(1)H and (13)C NMR spectra of two series of malononitrile-based merocyanines, which possess positive and negative solvatochromism have been in detail investigated in low polar chloroform and polar dimethyl sulfoxide (DMSO). Careful attribution of signals in spectra has been made with the help of two-dimensional NMR experiments (COSY, NOESY, HMBC, and HMQC). Hence, the dependence of merocyanines electronic structure on their chemical structure and solvent nature has been studied by this powerful method. It has been shown that there exists a good correlation between the calculated charges on carbon atoms of a polymethine chain and their chemical shifts in (13)C NMR spectra. The influence of solvent polarity on bond orders for dyes with positive and negative solvatochromism is also observed. The comparison of (13)C NMR spectra of merocyanines and corresponding parent ionic dyes allows to determine their sign of solvatochromism irrespectively of electronic spectra, and also to find the key atoms of chromophore whose signals in (13)C NMR spectra are most informative.     

Semiempirical and DFT computations of the influence of Tb(III) dopant on unit cell dimensions of cerium(III) fluoride

Several computational methods, both semiempirical and ab initio, were used to study the influence of the amount of dopant on crystal cell dimensions of CeF₃ doped with Tb³⁺ ions (CeF₃:Tb³⁺). AM1, RM1, PM3, PM6, and PM7 semiempirical parameterization models were used, while the Sparkle model was used to represent the lanthanide cations in all cases. Ab initio calculations were performed by means of GGA+U/PBE projector augmented wave density functional theory. The computational results agree well with the experimental data. According to both computation and experiment, the crystal cell parameters undergo a linear decrease with increasing amount of the dopant. The computations performed using Sparkle/PM3 and DFT methods resulted in the best agreement with the experiment with the average deviation of about 1% in both cases. Typical Sparkle/PM3 computation on a 2×2×2 supercell of CeF3:Tb3+ lasted about two orders of magnitude shorter than the DFT computation concerning a unit cell of this material. © 2014 Wiley Periodicals, Inc.     

Simple and convenient access to α,α,α-trisubstituted amides by double addition of Grignard reagents to acyl cyanohydrins

The double addition of Grignard (alkyl, aryl, alkenyl, alkynyl) reagents to acyl cyanohydrins was performed under unusually smooth conditions with a concomitant O-N acyl transfer, providing a very simple and general access to α,α,α-trisubstituted amides.     

The novel copper(I) π,σ-complexes with 1-(aryl)-5-(allylthio)-1H-tetrazoles: Synthesis,structure characterization,DFT-calculation and third-order nonlinear optics

The present work is directed toward preparation, structure and optical property characterization of tetrazole-containing Cu(I) compounds. By means of the alternating-current electrochemical technique copper(I) π,σ-compounds with 1-(4-methylphenyl)- (Matht), 1-(3-chloro-4-methylphenyl)- (Chmatht) and 1-[2-(trifluoromethyl)phenyl]- (Tfmatht) 5-(allylthio)-1H-tetrazoles were obtained in a single crystal form and structurally characterized by X-ray diffraction and Raman spectroscopy. Matht and Chmatht ligands, being attached to the Cu(I) through S-allylic C?=?C-bond and two tetrazole N-atoms, form stable centrosymmetric dimers [Cu₂(Matht)₂(H₂O)₂](BF₄)₂ and [Cu₂(Chmatht)₂(СlO₄)₂]. The presence of an electron acceptor trifluoromethyl group promotes formation of the monomeric [Cu(Tfmatht)₂]BF₄ and [Cu(Tfmatht)(NH₂SO₃)(MeOH)] compounds. The compounds were investigated by means of Raman spectroscopy, third-order nonlinear optics and DFT calculations.