X‐Ray Photoelectron Spectral Studies on Planar NiS4 and NiS2P2 Chromophores. Single Crystal X‐Ray Structural Study on [1, 4‐Bis(diphenylphosphino‐k,P, P')butane](piperidinecarbodithioato‐S,S')‐Nickel(II) Perchlorate

X‐ray photoelectron spectral study was made on the complexes Ni(nmedtc)₂( 1 ), [Ni(nmedtc)(PPh₃)₂]ClO₄( 2 ), [Ni‐(nmedtc)(dppe)]BPh₄( 3 ) (where nmedtc = N‐methyl, N‐ethanoldithiocarbamate, dppe = 1, 2‐bis(diphenylphosphino)ethane). The nickel 2p_3/2 binding energy values for chelated and free phosphine complexes are 854.0 and 854.1 eV which are significantly different from Ni2p_3/2 BE value of NiS₄ chromophore, indicating the relative dearth of electron density on Ni in NiS₂P₂ chromophores. The presence of two phosphine groups in NiS₂P₂ chromophore alleviates the electron density on the metal atom. More electron density is being pulled away from the metal atom in chelates than in the PPh₃ analogue. This observation is in line with solution studies by cyclic voltammetry. A one‐electron reduction potential was observed to be the minimum for NiS₂P₂ chromophores compared to the others. Also the crystal structure of the complex [Ni(pipdtc)(1, 4‐dppb)]ClO₄ (pipdtc^‐ = piperidinecarbodithioato anion, 1, 4‐dppb = bis(diphenylphosphino)butane) prepared by the reaction between Ni(pipdtc)₂, NiCl₂�6₂2O, and 1, 4‐dppb in CH₃CN‐CH₃OH is reported.     

Crystal Structure Studies of Two Regioisomers of Bromo-4-Aryloxymethylcoumarins

Abstract  

The 4-(2-bromo-4-methyl-phenoxymethyl)-6-methylcoumarin (1) have been synthesized from bromination of corresponding 4-aryloxymethyl coumarin, which is a regioisomer of 4-(2-bromo-4-methyl-phenoxymethyl)-7-methylcoumarin (2) (CCDC-695895). The compound 1 crystallizes with triclinic space group P-1, a = 8.0943(3) ?, b = 9.3502(3) ?, c = 10.1476(4) ?, α = 90.234(2)°, β = 94.065(2)°, γ = 95.106(2)°, Z = 2 and compound 2 crystallizes with monoclinic space group P2₁/n, a = 8.465(5) ?, b = 13.649(5) ?, c = 13.304(5) ?, α = 90.000(5)°, β = 90.740(5)°, γ = 90.000(5)°, Z = 4. Both the compounds are planar with variation in their intermolecular hydrogen bonds between C–H···O and C–H···π.     

Chemoselective synthesis and spectral studies of N-thiocyanatoacetyl derivatives of 3-alkyl-2,6-diarylpiperidin-4-ones

A series of N–thiocyanatoacetyl derivatives of 3–alkyl–2,6–diarylpiperidin–4–ones has been synthesized by the reaction between the N–chloroacetyl derivatives of the respective piperidin–4–ones and the ambident thiocyanate nucleophile. The synthesized compounds have been characterized through FT–IR, ¹H, ¹³C, ¹H–¹H COSY, ¹H–¹³C COSY and NOESY spectra. The spectral data reveal the conformational priority of the six-membered heterocyclic ring.     

The characterisation of the smallest two fold blocking sets in PG(<Emphasis Type="Italic">n</Emphasis>, 2)

We classify the smallest two fold blocking sets with respect to the (n−k)-spaces in PG(n, 2). We show that they either consist of two disjoint k-dimensional subspaces or are equal to a (k + 1)-dimensional space minus one point.     

Spin-polarized surface states on Fe-deposited Au(111) surface: A theoretical study

We have studied electronic structure of Fe-deposited Au(111) by performing ab initio density functional theory calculations. We find that the magnetic moment on the deposited Fe layer is enhanced as compared to that in bulk iron. We observe a large number of new states on the Fe-deposited surface — one of which is in the majority spin channel having similar dispersion to that on the clean surface, and others in the minority spin channel. The effective mass of electrons in surface states near the Fermi level increases on Fe deposition. The electronic properties are found to be insensitive to the stacking of near-surface layers. We need to use very thick slabs in our calculations to avoid splitting of surface states due to spurious interactions between the two surfaces of the slab. Using the local density of states profiles for different surface states, we conclude that in scanning tunneling microscope experiments one can detect two of the surface states — one in the majority channel below the Fermi level, and another in the minority channel appearing just above the Fermi energy. We compare our results to those from scanning tunneling spectroscopy experiments.     

Incomplete fusion reactions: Analysis of excitation functions and recoil range distributions in 16O + 51V

Incomplete fusion reactions were investigated by measuring the excitation functions of nine evaporation residues in ¹⁶O + ⁵¹V reaction in the beam energy 4-6 MeV/amu, using the well-known recoil catcher technique and gamma-ray spectrometry. The experimental data were compared with that obtained from Monte Carlo simulation calculations using the PACE2 code. The results indicate the presence of incomplete fusion process in the production of two alpha emission products. This was further confirmed by the measurement of recoil range distribution of these isotopes at 96 MeV beam energy. Calculations of the average angular momentum associated with these products revealed the peripheral nature of these ICF reactions. Received: 20 June 2001 / Accepted: 11 September 2001     

Two colour multiphoton ionization spectroscopy of uranium from a metastable state

Using two pulsed tunable dye lasers, a two colour multiphoton ionization process has been utilised to explore the higher energy levels of uranium. One hundred and thirty eight new UI levels have been observed in the 37540–38420 cm^–1 region. J assignments of these levels have been suggested on the basis of their excitation from intermediate levels with known and contiguous J values. In eight cases the J assignments are unique.     

A C6, C7 Oxygen Functionalized Intermediate for the Synthesis of Forskolin: Stereochemical Control in an Intramolecular Diels-Alder Reaction

Stereospecific intramolecular Diels-Alder reactions of aldehydes 3a and 3b afford lactones 4 and 5, respectively. The mechanism of the reactions is considered. Lactone 4 is elaborated further to provide acetonide 14b, an important intermediate in an approach to the synthesis of forskolin (1).