Complexes of nickel(II) with substituted thioureas

1968 ◽  
Vol 46 (20) ◽  
pp. 3119-3128 ◽  
Author(s):  
R. A. Bailey ◽  
Terry Roy Peterson
Keyword(s):  
Excited State ◽  
Ground State ◽  
Singlet Ground State ◽  
Methyl Ethyl ◽  
Triplet Excited State ◽  
Magnetic Studies ◽  
Distorted Octahedral

A series of Ni(II) complexes with methyl-, ethyl-, and sym-dimethyl-, sym-diethyl-, and sym-di-n-butyl- thioureas and halide, perchlorate, and thiocyanate anions have been prepared and characterized. Spectral and magnetic studies show that compounds NiL4X2 (L = N,N′-dimethyl and N,N′-diethylthiourea, X = halide) are tetragonally distorted octahedral species with a singlet ground state and a thermally populated triplet excited state. The remaining compounds are octahedral. Infrared evidence shows sulfur bonding of the disubstituted ligands to the metal, but suggests nitrogen coordination of the methylthiourea compounds.

Forbidden Electronic Transitions between the Singlet Ground State and the Triplet Excited State of Pt(II) Complexes

1998 ◽  
Vol 37 (14) ◽  
pp. 3588-3592 ◽  
Author(s):  
Greg Y. Zheng ◽  
D. Paul Rillema ◽  
Jeff DePriest ◽  
Clifton Woods
Keyword(s):  
Excited State ◽  
Ground State ◽  
Electronic Transitions ◽  
Singlet Ground State ◽  
Triplet Excited State

EXTENSION OF ENERGY DENSITY ANALYSIS TO TREATING CHEMICAL BONDS IN MOLECULES

2005 ◽  
Vol 04 (01) ◽  
pp. 317-331 ◽  
Author(s):  
HIROMI NAKAI ◽  
YASUAKI KIKUCHI
Keyword(s):  
Excited State ◽  
Energy Density ◽  
Ground State ◽  
Present Method ◽  
Chem Phys ◽  
Singlet Ground State ◽  
Chemical Bonds ◽  
Triplet Excited State ◽  
Hartree Fock ◽  
Density Analysis

We have extended the method of energy density analysis (EDA), originally proposed by Nakai (Chem Phys Lett363:73, 2002), to treat chemical bonds in molecules. The present method, termed "Bond-EDA", partitions the total energy calculated by the Hartree–Fock method not only into atomic regions, but also bond regions. Numerical applications of Bond-EDA are carried out for ethane and ethylene. The C – C and C – H dissociation processes are examined for both molecules. For ethylene, we further investigate the changes of chemical bonds by the excitation from the singlet ground state to the triplet excited state.

The mechanism of the photochemical cycloaddition reaction of N-benzoylindole with cyclopentene

1990 ◽  
Vol 68 (10) ◽  
pp. 1685-1692 ◽  
Author(s):  
Bimsara W. Disanayaka ◽  
Alan C. Weedon
Keyword(s):  
Excited State ◽  
Quantum Yield ◽  
Ground State ◽  
Mechanistic Model ◽  
Cycloaddition Reaction ◽  
Intersystem Crossing ◽  
Triplet Excited State ◽  
Excited State Lifetime ◽  
Yield Data ◽  
Counting Procedure

The mechanism of the photochemical cycloaddition reaction between N-benzoylindole, 1, and cyclopentene to give cyclobutane adducts 2 and 3 has been examined. The triplet excited state lifetime and quantum yield of intersystem crossing were determined for 1 as (2.8 ± 0.3) × 10−8 s and 0.39 ± 0.01, respectively, using the triplet counting procedure. In addition, the dependence of the quantum yield of cycloadduct formation upon the concentration of cyclopentene and upon the concentration of excited state quenchers has been determined. The results are used to propose a mechanistic model in which the triplet excited state of 1 reacts with cyclopentene to give a triplet 1,4-biradical intermediate. Following spin inversion the biradical intermediate reverts to the ground state starting materials or proceeds to the products 2 and 3; this partitioning, along with the quantum yield of intersystem crossing, gives rise to a limiting quantum yield of cycloaddition at infinite alkene concentration of 0.061. It is calculated that 84% of the biradical intermediates revert to the starting materials and 16% proceed to cycloadducts. The quantum yield data are also used to calculate two independent values of the rate constant for reaction of the triplet excited 1 with alkene; the values are (1.8 ± 0.1) × 107M−1 s−1 and (4.0 ± 0.8) × 106 M−1 s−1'. Some evidence for self quenching of the triplet excited state of 1 by ground state 1 was also observed. The quantum yield of intersystem crossing and the triplet excited state lifetime of 1 were found to vary with the solvent used; this is discussed in terms of the possible existence of a charge transfer triplet excited state. Keywords: indole, photocycloaddition, mechanism.

The high-order optical nonlinearity of 2,11,20,29-tetrabromo-2,3-naphthalocyanine iron

2018 ◽  
Vol 22 (09n10) ◽  
pp. 863-867
Author(s):  
Wang Zhang ◽  
Chunying He ◽  
Lining Zhang ◽  
Li Jiang ◽  
Yijun Yuan ◽  
...  
Keyword(s):  
Excited State ◽  
Cross Sections ◽  
Ground State ◽  
Nonlinear Refraction ◽  
Optical Nonlinearity ◽  
High Order ◽  
Saturable Absorption ◽  
Reverse Saturable Absorption ◽  
Triplet Excited State ◽  
First Excited State

A novel naphthalocyanine 2,11,20,29-tetrabromo-2,3-naphthalocyanine iron was synthetized. Its optical nonlinearity was investigated using the Z-scan technique. Reverse saturable absorption and high-order optical nonlinear refraction were detected. The absorption cross sections of the ground state, the singlet first excited state and the triplet first excited state were fitted to be 3.2 × 10[Formula: see text] cm[Formula: see text], 6.2 × 10[Formula: see text] cm[Formula: see text] and 4.6 × 10[Formula: see text] cm[Formula: see text], respectively. Fits also gave 1.17 × 10[Formula: see text] cm[Formula: see text] for the refractive volume of the ground state, 0.6 for the ratio of the refractive volume of the singlet first excited state to the ground state and 2.7 for the ratio of refractive volume of the first triplet excited state to the ground state.

Temperature effects on xanthone–β-cyclodextrin binding dynamics

2011 ◽  
Vol 89 (3) ◽  
pp. 395-401 ◽  
Author(s):  
Tamara C. S. Pace ◽  
Cornelia Bohne
Keyword(s):  
Excited State ◽  
Complex Formation ◽  
Ground State ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Equilibrium Constants ◽  
Dissociation Rate ◽  
Activation Entropy ◽  
Triplet Excited State ◽  
Dissociation Rate Constants

The complexation dynamics of the triplet excited state of xanthone with β-cyclodextrin were studied at various temperatures between 10 and 50 °C. Association and dissociation rate constants were determined using the laser flash photolysis quenching methodology with Cu2+ as a quencher. The rate constants for the association and dissociation of triplet xanthone with β-cyclodextrin increased with temperature, while the equilibrium constant for the triplet excited state remained relatively constant. Equilibrium constants for the ground-state complexation of xanthone with β-cyclodextrin were determined from fluorescence studies at various temperatures. The ground-state binding efficiency decreased with temperature and was markedly greater than that of the triplet excited state at all temperatures. The enthalpy and entropy for the β-cyclodextrin complex formation of the ground and triplet excited states fall on the enthalpy–entropy compensation relationship previously established for cyclodextrin complexes. The activation enthalpies for the association and dissociation rate constants for triplet xanthone are similar. The activation entropy is favorable for the association process, whereas a negative activation entropy was measured for the dissociation process, suggesting that solvation plays a key role in the complex formation between xanthone and β-cyclodextrin.

Stereochemical studies of the photochemical cycloaddition reaction of alkenes with N-benzoylindole and N-carboethoxyindole; evidence for biradical intermediacy

1991 ◽  
Vol 69 (7) ◽  
pp. 1171-1181 ◽  
Author(s):  
David J. Hastings ◽  
Alan C. Weedon
Keyword(s):  
Excited State ◽  
Rate Constant ◽  
Ground State ◽  
Addition Reaction ◽  
Cycloaddition Reaction ◽  
Adduct Formation ◽  
Quantum Yields ◽  
Triplet Excited State ◽  
Marked Contrast ◽  
Cis And Trans

The stereochemistries of the 2 + 2 cycloaddition products obtained from the photochemical addition reaction between N-benzoylindole or N-carboethoxyindole and the alkenes cyclopentene, cyclohexene, cycloheptene, cis- and trans-2-butene, and cis- and trans-4-octene are examined. The structures of the products are shown to be consistent with a photo-cycloaddition mechanism involving the intermediacy of triplet 1,4-biradical species. The quantum yields of adduct formation between N-benzoylindole and both cis- and trans-octene were measured as a function of alkene concentration. The results suggest that cis-octene reacts with the indole derivative's triplet excited state with a rate constant of (1.7 ± 0.3) × 107 M−1 s−1. The results are also consistent with the immediate products of this reaction being 1,4-biradicals, 98% of which revert to the ground state indole derivative and alkene, and only 2% of which proceed to cycloadduct. In marked contrast, the same treatment suggests that trans-octene reacts with the triplet excited state of N-benzoylindole with a rate constant estimated to be in the range of 1 × 106 and 6 × 105 M−1 s−1, and it appears that the 1,4-biradicals formed revert much less efficiently to the starting materials; it is estimated that between 67 and 100% of the 1,4-biradicals proceed to cycloadducts. In the reaction with cis-octene biradical reversion leads to the formation of trans-octene ("Schenk isomerization"); the quantum yield of this process is determined to be 0.074 ± 0.004, which may imply that approximately 75% of the biradicals collapse to cis-alkene and 25% collapse to the trans isomer. Key words: indole, photocycloaddition, 1,4-biradicals.

Structure of free complement wavefunction for the ground and the first excited state of helium atom

2017 ◽  
Vol 16 (06) ◽  
pp. 1750048
Author(s):  
Mohammad Mostafanejad
Keyword(s):  
Excited State ◽  
Symmetric Group ◽  
Helium Atom ◽  
Excited States ◽  
Ground State ◽  
Triplet Excited State ◽  
Ground State Wavefunction ◽  
First Excited State ◽  
Orbital Exponents ◽  
Elegant Form

We review the fundamental ideas of free complement (FC) method through its application on both ground and first excited states of helium atom. We have found that lower energies can be obtained with fewer number of terms in the FC expansion of the ground state wavefunction. In this case, the optimization of orbital exponents was not necessary for achieving spectroscopic accuracy, especially at higher orders where the structure of the FC wavefunction converges to that of the exact one. We have discovered that permanents naturally appear in the FC expansion of the first triplet excited state wavefunction. Including permanents in the FC expansion is shown to be energetically important for the first triplet excited state of helium atom whereas it is not computationally favorable at higher orders. Finally, considering the group theoretical properties of the symmetric group [Formula: see text] and using immanants, a compact and more elegant form for the FC expansion of the first triplet excited state of the helium atom is achieved.

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