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.

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.

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 analysis of a 2 A 1 - 2 B 1 electronic band system of the AsH 2 and AsD 2 radicals

1968 ◽  
Vol 305 (1481) ◽  
pp. 271-290 ◽  
Keyword(s):  
Excited State ◽  
Ground State ◽  
Flash Photolysis ◽  
Band System ◽  
Valence Angle ◽  
Electronic Transitions ◽  
Doublet State ◽  
Electronic Band ◽  
Asymmetric Rotor ◽  
Asymmetric Top

Two new band systems have been observed in absorption following flash photolysis of AsH 3 and AsD 3 , and are assigned to 2 A 1 - 2 B 1 electronic transitions of AsH 2 and AsD 2 . The origins of both systems are at 19905 cm -1 . The bands have the complex rotational structure associated with an asymmetric rotor. Rotational analyses have been carried out for three bands of the AsH 2 spectrum, leading to the following molecular parameters: ground state, r" 0 = 1.518 Å valence angle = 90° 44'; excited state, r' 0 = 1.48 Å, valence angle = 123° 0'. The parameters associated with rotation about the a inertial axis increase rapidly with increase in v' 2 . The spectrum shows doublet splittings of up to 41 cm -1 , and the excited state furnishes the first example of a doublet state of an asymmetric top molecule which shows substantial departures from Hund’s case ( b ).

THE ABSORPTION SPECTRUM OF BO2

1961 ◽  
Vol 39 (12) ◽  
pp. 1738-1768 ◽  
Author(s):  
J. W. C. Johns
Keyword(s):  
Absorption Spectrum ◽  
Excited State ◽  
Detailed Analysis ◽  
Ground State ◽  
Flash Photolysis ◽  
Electronic Transitions ◽  
Molecular Constants ◽  
Boron Trichloride ◽  
Symmetric Molecule ◽  
First Excited State

The boron flame bands have been observed in absorption during the flash photolysis of mixtures of boron trichloride and oxygen. Detailed analysis of the spectrum has shown that the bands arise from two electronic transitions in the linear symmetric molecule BO2, [Formula: see text] and A2Πu−X2Πg. The main molecular constants, in cm−1 except for r0, are summarized below:[Formula: see text]Both 2Π states show the Renner effect. In the ground state the Renner parameter, εω2, was found to be −92.2, whereas in the first excited state it is much smaller, −13.1 cm−1.

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.

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