Assembling Screws: Large Preference for the Homochiral Combination in the Proton-Bound Dimers of 1-Aza[6]helicene in the Gas Phase

By means of selective deuterium labeling combined with separation of enantiomers, chiral discrimination in the proton-bound dimers of 1-aza[6]helicene is probed by electrospray mass spectrometry. The analysis of the results reveals a pronounced preference for the formation of homochiral dimers (P,P and M,M) over the heterochiral variant (P,M)

Recent Progress in Asymmetric Synthesis

The most remarkable progress has been recorded recently in homogeneous enantioselective catalysis by chiral transition metal complexes, enzymes, and nonmetal organic catalysts

Biophysical and RNA interference inhibitory properties of oligonucleotides carrying tetrathiafulvalene groups at terminal positions

Oligonucleotide conjugates carrying a single functionalized tetrathiafulvalene (TTF) unit linked through a threoninol molecule to the 3′ or 5′ ends were synthesized together with their complementary oligonucleotides carrying a TTF, pyrene, or pentafluorophenyl group. TTF-oligonucleotide conjugates formed duplexes with higher thermal stability than the corresponding unmodified oligonucleotides and pyrene- and pentafluorophenyl-modified oligonucleotides. TTF-modified oligonucleotides are able to bind to citrate-stabilized gold nanoparticles (AuNPs) and produce stable gold AuNPs functionalized with oligonucleotides. Finally, TTF- oligoribonucleotides have been synthesized to produce siRNA duplexes carrying TTF units. The presence of the TTF molecule is compatible with the RNA interference mechanism for gene inhibition.The authors thank Dr. Anna Avi˜n´o for providing the nonmodified oligonucleotides 11–14.This researchwas supported by the European Commission (Grants FP7-FUNMOL 213382 and NMP4-LA-2011-262943, MULTIFUN), by the Spanish Ministry of Education (grant CTQ2010-20541, SAF2010-15440), the Generalitat de Catalunya (2009/SGR/208), the Czech Science Foundation (P207/10/2214), the Ministry of Education, Youth and Sports of the Czech Republic (7E09054), and the Institute of Organic Chemistry and Biochemistry AS CR (RVO: 61388963). The authors declare no conflict of interests.Peer reviewe

Interstrand interactions on DNA duplexes modified by TTF units at the 3′ or 5′-ends

Short DNA duplexes carrying TTF units at the same termini exhibit a high increase in melting temperature. When both TTF units were on opposite termini, salt-dependent aggregation is observed, yielding well defined spherical DNA supramolecular structures.This research was supported by the European Commission under Grant No. FP7-FUNMOL 213382, by the Spanish Ministry of Education (CTQ2010-20541), the Generalitat de Catalunya (2009/SGR/208), the Czech Science Foundation (P207/10/2214) and the Institute of Organic Chemistry and Biochemistry AS CR (this work is part of the Research Project Z4 055 0506). Dr. Radek Pohl is acknowledged for the NMR spectra measurement as well as the electron cryo-microscopy unit from CCiT of University of Barcelona for the use of the EM facility.Peer reviewe

Reaction of Isocyanate-Functionalised Silicon Wafers with Complex Amino Compounds

International audienc

On the Physicochemical Properties of Pyridohelicenes

International audienc

Two-photon absorption and two-photon circular dichroism of hexahelicene derivatives: a study of the effect of the nature of intramolecular charge transfer

International audienceHerein we report on the theoretical-experimental analysis of the one- and two-photon absorption and circular dichroism spectra of two intrinsically chiral aromatic molecules - hexahelicene derivatives - with helical chirality and intramolecular charge transfer (ICT). The primary outcomes of our investigation demonstrate that the TPA cross-section and the amplitude of the TPCD signal of this type of helicenes are strongly affected by the strength of the ICT and the nature of the extension of the electronic delocalization, i.e. beyond (EXO-ICT) or within (ENDO-ICT) the helicene core. These results were corroborated through the comparative theoretical analysis of the corresponding contributions of the magnetic dipole transition moment and the electric quadrupole transition moment to the TPA rotatory strength on a series of five similar helicene derivatives with different molecular electron delocalization disposition.Two-photon absorption (TPA) and two-photon circular dichroism (TPCD) spectra were obtained using the double L-scan technique over a broad spectral range (400 nm - 900 nm) using 90 fs pulses at a low repetition rate (2-50 Hz) produced by an amplified femtosecond system. The theoretical simulations were performed using modern analytical response theory within the Time-Dependent Density Functional Theory (TD-DFT) approach using B3LYP and CAM-B3LYP, and the aug-cc-pVDZ and 6-311++G(d,p) basis sets