Resonance Assisted Hydrogen Bonding Phenomenon Unveiled through Both Experiments and Theory: A New Family of Ethyl N-Salicylideneglycinate Dyes

Extensive experimental and theoretical investigations are reported on the nature of resonance-assisted hydrogen bonding phenomenon (RAHB) and its influence on photophysical properties of the newly designed dyes differing in donor–acceptor properties, namely ethyl N-salicylideneglycinate ( 1 ), ethyl N-(5-methoxysalicylidene)glycinate ( 2 ), ethyl N-(5-bromosalicylidene)glycinate ( 3 ) and ethyl N-(5-nitrosalicylidene)glycinate ( 4 ). All compounds are thermochromic in the solid state and they contain a typical intramolecular O−H⋅⋅⋅N hydrogen bond formed between the hydroxyl hydrogen atom and the imine nitrogen atom, yielding the enol form in the solid state. It is unveiled, that the magnitude of RAHB effect fine tunes the strength of the O−H⋅⋅⋅N bonding and accordingly the relative populations of the enol, cis-keto and trans-keto forms leading to variation of the photophysical properties of 1 – 4 . It is determined, that the electron-withdrawing NO₂ in 4 amplifies the most RAHB effect causing the breaking of the O−H⋅⋅⋅N hydrogen bond and accordingly formation of the dominant cis-keto isomer in both the solid state and EtOH. To this end, the UV/Vis spectra of 1 – 3 in EtOH revealed the exclusive presence of the enol form, while the prevalent contribution of the cis-keto form was found for 4 . Furthermore, only compound 4 is emissive in the solid state in ambient condition due to dual emission arising from the cis-keto* and trans-keto* forms, while 2 was found to be highly emissive in EtOH. It is revealed qualitatively and quantitatively, based on the ETS-NOCV charge and energy decomposition scheme and the EDDB population-based method, that RAHB is strongly a non-local phenomenon based on electrons pumping or sucking through both the π- and σ-channels, which accordingly exerts chemical bonding changes at both the phenyl ring and predominantly a distant O−H⋅⋅⋅N area.     

Photophysics of Titania Nanoparticle/Quantum Dot Hybrid Structures

Optics and Spectroscopy - The efficiency of the electron transfer in hybrid structures based on quantum dots of different architectures was studied. Electron transfer efficiency was estimated by...     

Potential energy of interaction between a fast multiply charged ion and crystal atoms with regard for the Pauli principle

Expressions for the potential energy of interaction between a fast neutral atom or a multiply charged ion and a crystal atom are obtained, both with and without regard for the Pauli principle. Results from computer simulation of the heating of silver ions with a fixed value of the charge state in passing through the (110) planar channel of a silicon crystal are presented. It is shown that the rate of dechanneling can be estimated by the form of the potential energy of interaction of an incident ion with a continuous potential of the planar crystal channel.     

Effects of <Emphasis Type="Italic">C</Emphasis>-, <Emphasis Type="Italic">P</Emphasis>-, <Emphasis Type="Italic">T</Emphasis>-symmetries violation in the polarized elastic electron-proton electroweak scattering

Analytical expressions are obtained for the angular distributions and spin asymmetries of the processes of elastic electromagnetic and electroweak scattering of high energy electrons on polarized/unpolarized proton target with account of C-, P- and T/CP-invariance violating anapole and electric dipole moments, as well as neutral weak electric, magnetic and axial form factors of the proton. Behavior of the P- and T- odd spin asymmetries is studied in dependence of the electron’s energy and scattering angle and proton form factors parameters.     

Microscopic origins of the anomalous melting behavior of sodium under high pressure

X-ray diffraction experiments have shown that sodium exhibits a dramatic pressure-induced drop in melting temperature, which extends from 1000 K at ~30 GPa to as low as room temperature at ~120 GPa. Despite significant theoretical effort to understand the anomalous melting, its origins are still debated. In this work, we reconstruct the sodium phase diagram by using an ab initio quality neural-network potential. Furthermore, we demonstrate that the reentrant behavior results from the screening of interionic interactions by conduction electrons, which at high pressure induces a softening in the short-range repulsion.     

Synthesis and characterization of crown ether–containing N‐phosphorylated thioureas RC(S)NHP(O)(OiPr)2 (R = 1‐aza‐15‐crown‐5, 1‐aza‐12‐crown‐4) and their Co(II) and Ni(II) complexes

The reaction of the lithium salts of N‐phosphorylated thioureas RC(S)NHP(O)(OiPr)₂ (R = 1‐aza‐15‐crown‐5, HL ^I ; 1‐aza‐12‐crown‐4, HL ^II ) with Co(II) or Ni(II) leads to the chelate complexes [ ML ^I,II ₂ ]. The metal center is found in a tetrahedral ([ CoL ^I,II ₂ ]) or square planar ([ NiL ^I,II ₂ ]) O₂S₂ environment formed by the CS sulfur atoms and the PO oxygen atoms of two deprotonated ligands L . The molecular structure of [ CoL ^I ₂ ] was elucidated by X‐ray diffraction and the extraction properties of HL ^I,II and [ ML ^I,II ₂ ] toward alkali metal and ammonium picrates were investigated. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:486–491, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20637     

Synthesis and characterization of silver(I) complexes with N‐thiophosphorylated thiobenzamide or thiourea and phosphines

A reaction of the potassium salts of RC(S)NHP(S)(OiPr)₂ (R = PhNH, HL ^I; Ph, HL ^II) with a mixture of AgNO₃ and Ph₂P(CH₂)_{1 − 3}PPh₂ or Ph₂P(C₅H₄FeC₅H₄)PPh₂ in aqueous EtOH/CH₂Cl₂ leads to [Ag₂(Ph₂PCH₂PPh₂)₂L^INO₃] ( 1 ), [Ag{Ph₂P (CH₂)₂PPh₂}L^I,II] ( 2, 6 ), [Ag{Ph₂P(CH₂)₃PPh₂}L^I,II] ( 3, 7 ), [Ag{Ph₂P(C₅H₄FeC₅H₄)PPh₂}L^I,II] ( 4, 8 ), and [Ag₂(Ph₂PCH₂PPh₂)L^II₂] ( 5 ) complexes. The structures of these compounds were investigated by ¹H and ³¹P{¹H} NMR spectroscopy and elemental analyses. It was established that the binuclear complexes 1 and 5 are luminescent in the solid state at ambient conditions. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:386–391, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20627     

Novel water-soluble quaternary piperazine derivatives of chitosan: synthesis and characterization

Novel synthesis methods for the preparation of quaternary piperazine derivatives of chitosan were developed. Quaternary ammonium moiety can be selectively inserted into either one or both of the piperazine nitrogens, yielding structurally uniform chitosan derivative structures. Water-soluble end products were thoroughly characterized with FT-IR, 1H NMR, 13C NMR and 2D 1H-13C HSQC NMR. The molecular weights of the end products were determined by GPC with triple detection.