DFT and DFT-D studies on molecular structure of double-decker phthalocyaninato-terbium(III) complex

A molecular structure of a double-decker phthalocyaninato-terbium(III) anion (TbPc₂^?) is optimised by density functional theory (DFT) and DFT with a dispersion interaction (DFT-D) method. The DFT-D method such as B3LYP-D and B97-D functional sets estimates phthalocyaninato (Pc) ions to be planar although B3LYP and PBE1PBE make them concave. In addition, the planar structure corresponds to an experimental X-ray crystallographic result. On the other hand, an optimised geometry of Pc^2? dimer by B3LYP-D estimates the convex Pc^2? structure due to the dispersion interaction between outer aromatic rings. These results suggest the importance of the dispersion interaction for the structure of TbPc₂^?.     

13C NMR Chemical Shifts Substituent Effects of (E)- and (Z)-N-ethyl-N-Methylamides

Carbon-13 NMR chemical shifts of a series of (E)- and (Z)-N-ethyl-N-methylamides [RC(O)NEtMe, R=H, Me, Et, i-Pr, t-Bu, CF₃, ClCH₂, Cl₂CH, Cl₃C, BrCH₂, Br₂CH, Br₃C and ICH₂] are reported. The α-carbon and carbonyl carbon chemical shifts are correlated with the empirical α-substituent effect and Charton's electrical parameter ([sgrave]_I), respectively. The N-alkyl carbon resonances were attributed mainly to the γ- and δ-effects of R.     

Simultaneous observation of low temperature 4f-4f and 3d-3d emission spectra in a series of Cr(III)(ox)Ln(III) assembly

We report here the low temperature emission spectra in the heterometal dinuclear 3d-4f assembled molecular system [(acac)₂Cr^III(μ-ox)Ln^III(HBpz₃)₂] (Cr(ox)Ln:acac⁻=acetylacetonate, ox²⁻=oxalate, HBpz₃⁻=hydrotris(pyrazol-1-yl)borate; Ln=La, Nd, Ho, Er , Tm and Yb) in comparison with those of Na[Cr(acac)₂(ox)] and [(HBpz₃)₂Ln(μ-ox)Ln(HBpz₃)₂](Ln=Nd and Er). From 10 to 150 K the Cr(ox)Ln complexes show a broad emission band around 800 nm from the ²E state of Cr(III) moiety. At room temperature no ²E-⁴A₂ emission was observed in the Cr(ox)Ln except for the La and Lu complexes. On warming from 10 to 300 K rapid quenching of the ²E-⁴A₂ emission of Cr(III) is suggested to result from the energy transfer from Cr to Ln in the Cr(ox)Ln. The excitation spectra and the life-time were also measured with monitoring the 4f-4f emission peaks of the Cr(ox)Yb complex.     

Enhanced fluorescence of Tb(III), Dy(III) perchlorate by salicylic acid in bis(benzoylmethyl) sulfoxide complexes and luminescence mechanism

Two novel ternary rare earth perchlorate complexes had been synthesized by using bis(benzoylmethyl) sulfoxide as first ligand (L=C₆H₅COCH₂SOCH₂COC₆H₅), salicylic acid as second ligand (L^′=C₆H₄OHCOO⁻). The compounds were characterized by elemental analysis, TG-DSC and molar conductivities in DMF solution. The composition was suggested as [REL₅L′](ClO₄)₂·nH₂O (RE=Tb, Dy; n=6, 8 ). Based on IR, ¹HNMR and UV spectra, it showed that the first ligand, bis(benzoylmethyl) sulfoxide (L), bonded with Tb(III), Dy(III) ions by the oxygen atom of sulfinyl group. The second ligand, salicylic acid group (L′), not only bonded with RE(III) ions by one oxygen atom of carboxyl group but also bonded with RE(III) ions by oxygen atom of phenolic hydroxyl group. In bis(benzoylmethyl) sulfoxide system, fluorescent spectra of the complexes showed that the luminescence of Tb(III), Dy(III) ions was enhanced by the second ligand salicylic acid. The ternary complexes had stronger fluorescence than the binary ones where only bis(benzoylmethyl) sulfoxide acted as ligand. Phosphorescent spectra of the two ligands indicated that the coordination of salicylic acid resulted in the matching extent increasing between the triplet state of ligand and excited state of the rare earths. The relationship between fluorescence lifetime and fluorescence intensity was also discussed.     

A method for C(alpha) direct-detection in protonless NMR

Attempts are made to efficiently decouple (13)C nuclei without significant loss of coherence during the application of the decoupling package. Such attempts are based on the S(3)E spin-state selection method. A newly developed double S(3)E (DS(3)E) is particularly efficient for C(alpha) detection for proteins as large as 480 kDa.     

Natural abundance (17)O NMR spectroscopy of rat brain in vivo

Oxygen is an abundant element that is present in almost all biologically relevant molecules. NMR observation of oxygen has been relatively limited since the NMR-active isotope, oxygen-17, is only present at a 0.037% natural abundance. Furthermore, as a spin 5/2 nucleus oxygen-17 has a moderately strong quadrupole moment which leads to fairly broad resonances (T(2)=1-4 ms). However, the similarly short T(1) relaxation constants allow substantial signal averaging, whereas the large chemical shift range (>300 ppm) improves the spectral resolution of (17)O NMR. Here it is shown that high-quality, natural abundance (17)O NMR spectra can be obtained from rat brain in vivo at 11.74 T. The chemical shifts and line widths of more than 20 oxygen-containing metabolites are established and the sensitivity and potential for (17)O-enriched NMR studies are estimated.     

Assignment of the 1H and 13C NMR Chemical Shifts of (3,4-Dihydro-2H-pyran-5-yl)-oxo-acetic Acid Methyl Ester Using the Two Dimensional HMBC Technique

The identification of (3, 4-dihydro-2H-pyran-5-yl)-oxo-acetic acid methyl ester has been realized by combination of two dimensional HETCOR and HMBC techniques. ¹³C and ¹H chemical shifts asignements are described.     

Hydroxyl Substituent Chemical Shift (SCS) Effects in Alcohols: The 17O NMR of Diols

The ¹⁷O NMR spectra for a series of saturated diols were investigated. From these studies both hydroxyl induced substituent chemical shift (SCS) effects of hydroxyl oxygen ¹⁷O NMR chemical shifts were determined. In addition, linear correlations between the ¹⁷O chemical shift of the hydroxyl oxygen (ROH) and the ¹³C chemical shift for the methyl group in the corresponding hydrocarbon (RCH₃) were obtained.

     

The Prediction of the 13C NMR Signal Positions in Substituted Naphthalenes,Part 2: The Use of Statistical Substituent Chemical Shift (SSCS) Values

The prediction of the ¹³C NMR signals for derivatives of naphthalene has been investigated using statistical Substituent Chemical Shift (SSCS) values. For α-derivatives the model had a correlation coefficient of observed versus predicted line positions of r=.98 with an standard deviation of 2.1ppm while in the β case r=.98 with the standard deviation being 2.0ppm. Prediction of the 9 and 10 positions had an r=.93 with the standard deviation being 1.5ppm. The data base consisted of 5250 signals from 525 naphthalene derivatives.     

A 1H NMR Study of Palladium(II) Coordination Compounds with 2-Aminooxypropanoic Acid and Its Methyl Ester

The ¹H NMR spectra of 2-aminooxypropanoic acid, its methyl ester and their hydrochlorides have been inspected. The interaction of these ligands with palladium(II) has been investigated in deuterium oxide and in dimethyl sulfoxide. The metal has been found to form a chelate with the acid, whereas its esters coordinated to the metal through the nitrogen atom of the aminooxy group only. In dimethyl sulfoxide, also the methyl esters and hydrochlorides of 2-aminooxybutanoic, 2-aminooxy-3-methylpentanoic,as well as the ester of 2-aminooxyhexanoic and the hydrochoride of the ester of 2-aminooxy-3-phenylpropanoic acid have been studied.     

Study on Stereochemical Activity of Lone Pair Electrons in Sulfur and Halogen Coordinated Antimony(III) Complexes by 121Sb Mössbauer Spectroscopy

We have measured ¹²¹Sb Mössbauer spectra at 20 K for 52 compounds of antimony(III). An Sb(III) atom with the electron configuration [Kr] 4d ¹⁰5s ² has a lone pair electrons. The stereochemical property of the lone pair has been found to depend very much on the kinds of atoms surrounding the antimony atom and the configurations of the coordinating atoms.     

Molecular Spectral Analysis and Ab Initio Calculations of bis(3-aminopyridinium) Tetrachlorocuprate (II), 3-Ammoniumpyridinium Tetrachlorocuprate (II), and bis(3-aminopyridinium) Hexachlorodicuprate (II)

The aromatic character, distortion, and stabilization as a result of single and double protonation of 3-aminopyridine like three different complex salts were studied by infrared-, ultraviolet spectral analysis, proton nuclear magnetic resonance, and quantum chemical ab initio calculations. Linear-dichroic infrared spectroscopy was applied for identification of the infrared bands. The correlation structure-spectroscopic properties of the model systems are determined: bis(3-aminopyridinium) tetrachlorocuprate (II) salt, where the ring nitrogen atom participates in protonation; 3-ammoniumpyridinium tetrachlorocuprate (II) salt, where both nitrogen atoms are protonated; and a complex with copper (II) bis(3-aminopyridinium) hexachlorodicuprate (II), where the metal ion is coordinated through amino group.     

Synthesis and Spectroscopic Properties of Iron(H) Complex with Sterically Encumbered Thiolate Ligand: 2,4,6-Triphenylbenzenethiolate

Abstract

Novel iron(II) complex of 2,4,6-triphenylbenzenethiolate (tpbt) was synthesized by ligand exchange reaction of (Et₄N)2[Fe^II(S-t-Bu)₄] with tpbt-H. The complex shows absorption maxima at 277 nm (36500 M^?1cm^?1) and 367 nm (22800 M^?1 cm^?1), and Fe²⁺/Fe³⁺ redox potential at-0.78 V vs SCE in acetonitrile. While in tetrahydrofuran solution, the complex is found to be unstable and form a Fe(II) complex with low coordination number.     

Group theoretical aspects ofU B(6) ⊗U F(20) symmetry limits of IBFM related to theU B(5) andO B(6) limits of IBM

TheU ^B(6)⊗U ^F(20) Bose-Fermi dynamical symmetry of interacting boson-fermion model arises when the odd nucleon occupies single particle orbits withj=1/2, 3/2, 5/2, and 7/2. The subgroup structures ofU ^B(6)⊗U ^F(20) related to theU ^B(5) andO ^B(6) limits of sdIBM (U ^B(6)) are analysed. Broadly speaking,U ^B(6)⊗U ^F(20) admitsU ^BF(5)⊗U _s ^F (4), Spin^BF(5)⊗U _k ^F (5) andU ^BF(5)⊗U _s ^F (2) limits withU ^B(5) core and Spin^BF(6),O ^BF(5)⊗U _s ^F (4), Spin^BF(6)⊗U _k ^F (5) andO ^BF(6)⊗U _s ^F (2) limits withO ^B(6) core respectively. For each of these seven symmetry limits, group chains, quantum numbers labelling the basis states, generators and Casimir operators for the various subgroups and energy formulas are given. Recoupling coefficients (reduced Wigner coefficients) for constructing wavefunctions of low-lying states are tabulated and these will allow (together with sdIBMU ^B(5) andO ^B(6) limit results) one to calculateB(E2)’s,B(M1)’s, one and two nucleon transfer strengths etc. in the seven symmetry limits. Experimental examples for theU ^B(6)⊗U ^F(20) symmetry limits are briefly discussed.     

Investigation of photophysical properties of mer-tris(8-hydroxyquinolinato) aluminum (III) and its derivatives: DFT and TD-DFTcalculations

Optimized structures and photophysical properties of mer- and fac-Alq₃ have been generated by using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). Investigating the substitution effect in the Alq₃ derivatives, the role of the electron-donating (CH₃- and NH₂-) and electron-withdrawing (F-, CN-, NO₂- and phenyl-) groups with 2- to 7-substitution have been analyzed. According to the calculation results, the 4- and 5- substituted Alq₃ exhibit an apparent spectral shift relative to the non-substituted Alq₃. The HOMO, LUMO, E_g (the energy gap between LUMO and HOMO), (maximum absorption wavelength) and f (the relative oscillator strength) of mer-Alq₃ with the 4- or 5-phenyl substitution on the quinoline ligand in the ground electronic state were calculated by using the DFT/B3LYP/6-31G(d) and TD-DFT methods. 5-phenyl substituted mer-Alq₃ with an electron-donating substituent showed an increase in the π-delocalization as compared to the 4-phenyl substituted mer-Alq₃ derivatives. Similarly, 4-phenyl substituted mer-Alq₃ with electron-withdrawing substituents also exhibits increased π-delocalization in the pyridine ring as compared to the non-substituted Alq₃. Replacing the CH group at the 4, 5 and 4,5 positions of the quinoline ligand of mer-Alq₃ with the aza group (nitrogen atom) gives three Alq₃ analogous: AlX₃, Al(NQ)₃ and Al(NX)₃; the calculated energy gap E_g of these derivatives decreases in the order Al(NQ)₃>Al(NX)₃>AX₃. Four quinoline with group III metals Mq₃ complexes were investigated for the photophysical properties; the calculated energy gap E_g decreases in the order Tlq₃>Inq₃>Gaq₃>Alq₃. The photophysical properties of 4-hydroxy-8-methyl-1,5-naphthyridine (mND) chelated with group III metals (MmND₃ complexes) were investigated also; their calculated E_g have the opposite order as those of Mq₃ complexes.     

Spin States of Iron(III) in Highly Saddled Dodecaphenylporphyrin Complexes

The alignment correlation term in the β-decay angular distribution from purely nuclear spin aligned ²⁰Na has been measured for the first time. The final objective is to test the G parity symmetry, one of the fundamental symmetry in the weak nucleon current. For artificial creation of the alignment, the knowledge of the hyperfine interaction of ²⁰Na implanted in a single-crystal ZnO was utilized. *Research Abroad, Japan Society for the Promotion of Science     

Assignment of the 1H and 13C Spectra of 5-Methylthio-4H-1-(p-R1-phenyl)-3a-(p-R2-phenyl)-3a,4-dihydro (1,2,4) oxadiazolo(4,5-a), 1,5-benzodiazepines using 2D NMR Spectroscopy.

The ¹H NMR spectra of the title benzodiazepines derivatives is highly congested because all the protons are in aromatic enviroment so many proton signals remain overlap even 300 MHz or higher fields. With this in mind, the assignment of the ¹H and ¹³C spectra of these compounds obtained using COSY, NOESY, HMQC and HMBC experiments is reported.     

Two-Dimensional NMR Studies of Triterpenoid Glycosides. II)- 1 H NMR Assignment of Arvensoside A and B,Calenduloside C and D

During the investigation of the glycosidic constitutents of Calendula arvensis L. we isolated the previously reported Arvensoside A, Arvensoside B, Calenduloside C and Calenduloside D. The complete assignment ¹H NMR spectra of these compounds was achieved through the concerted application of 2D-homonuclear chemical shift correlations. Calenduloside C and Calenduloside D were isolated for the first time from the fresh aerial parts of Calendula arvensis L.     

Kinetics and mechanism of uncatalysed and ruthenium(III) catalysed oxidation of allyl alcohol by diperiodatoargentate(III) in aqueous alkaline medium

The oxidation of allyl alcohol by diperiodatoargentate(III) (DPA) is carried out both in the absence and presence of ruthenium(III) catalyst in alkaline medium at 298 K and a constant ionic strength of 1.1 mol dm^?3 was studied spectrophotometrically. The oxidation products in both the cases were acrolein and Ag(I), identified by spectral studies. The stoichiometry is same in both the cases, that is, [AA]/[DPA] = 1:1. The reaction shows first order in [DPA] and has less than unit order dependence each in both [AA] and [Alkali] and retarding effect of [IO] in both the catalysed and uncatalysed cases. The order in [Ru(III)] is unity. The active species of DPA is understood to be as monoperiodatoargentate(III) (MPA) in both the cases. The uncatalysed reaction in alkaline medium has been shown to proceed via a MPA–allyl alcohol complex, which decomposes in a rate determining step to give the products. In catalysed reaction, it has been shown to proceed via a Ru(III)‐allyl alcohol complex, which further reacts with one molecule of MPA in a rate determining step to give the products. The reaction constants involved in the different steps of the mechanisms were calculated for both reactions. The catalytic constant (K_c) was also calculated for catalysed reaction at different temperatures. The activation parameters with respect to slow step of the mechanisms were computed and discussed for both the cases. The thermodynamic quantities were also determined for both reactions. Copyright © 2007 John Wiley & Sons, Ltd.