Vibrational dependence of electronic nonradiative processes in the state of and

1984 ◽  
Vol 62 (12) ◽  
pp. 1361-1368 ◽  
Author(s):  
D. Winkoun ◽  
D. Chapoulard ◽  
G. Dujardin ◽  
S. Leach
Keyword(s):  
Vibrational Mode ◽  
Spectroscopic Properties ◽  
Quantum Yields ◽  
Electronic Relaxation ◽  
Matrix Elements ◽  
Relaxation Rates ◽  
Fluorescence Quantum Yields ◽  
Fluorescence Photon ◽  
Mode Selectivity ◽  
Nonradiative Processes

Vibrational mode selective, radiationless transitions have been sought in the [Formula: see text] states of [Formula: see text] and [Formula: see text] by determining the radiative kr(ν′) and nonradiative knr(ν′) rates of electronic relaxation of energy selected vibronic levels of these cations. The relaxation rates were derived from measurements of ion fluorescence quantum yields and lifetimes using a photoelectron-fluorescence photon delayed coincidence apparatus, described in the text, in which the ions are formed by direct photoionization. Mode selective behavior is confirmed for the ν1 and ν2 modes of the [Formula: see text] state of [Formula: see text], previously studied by a threshold photoelectron-fluorescence photon coincidence method in which photoion formation involved auto-ionization as well as direct photoionization. In the case of the ν3 and ν4 modes of [Formula: see text], knr(ν′) was found to depend only on the excess energy Eν′ in the [Formula: see text] state and not on the particular mode optically excited. The absence of mode selectivity in this cation could be due to very rapid vibrational redistribution, but more probably results from similar-valued nonradiative coupling matrix elements of vibronic levels involving ν3 and (or) ν4 modes for a given value of Eν′. This is shown to be consistent with the known spectroscopic properties of [Formula: see text].

scholarly journals Theoretical and Experimental Investigations of Large Stokes Shift Fluorophores Based on a Quinoline Scaffold

Molecules ◽  
2020 ◽  
Vol 25 (11) ◽  
pp. 2488
Author(s):  
Barbara Czaplińska ◽  
Katarzyna Malarz ◽  
Anna Mrozek-Wilczkiewicz ◽  
Aneta Slodek ◽  
Mateusz Korzec ◽  
...  
Keyword(s):  
Theoretical Calculations ◽  
Stokes Shift ◽  
Visible Region ◽  
Spectroscopic Properties ◽  
Cellular Membrane ◽  
Structural Features ◽  
Quantum Yields ◽  
Experimental Investigations ◽  
Case Scenario ◽  
Fluorescence Quantum Yields

A series of novel styrylquinolines with the benzylidene imine moiety were synthesized and spectroscopically characterized for their applicability in cellular staining. The spectroscopic study revealed absorption in the ultraviolet–visible region (360–380 nm) and emission that covered the blue-green range of the light (above 500 nm). The fluorescence quantum yields were also determined, which amounted to 0.079 in the best-case scenario. The structural features that are behind these values are also discussed. An analysis of the spectroscopic properties and the theoretical calculations indicated the charge-transfer character of an emission, which was additionally evaluated using the Lippert–Mataga equation. Changes in geometry in the ground and excited states, which had a significant influence on the emission process, are also discussed. Additionally, the capability of the newly synthesized compounds for cellular staining was also investigated. These small molecules could effectively penetrate through the cellular membrane. Analyses of the images that were obtained with several of the tested styrylquinolines indicated their accumulation in organelles such as the mitochondria and the endoplasmic reticulum.

Ground- and Excited-State Absorption Spectra of 9-Acetoxy-10(4´-Acetoxy)phenylanthracenes

1986 ◽  
Vol 41 (10) ◽  
pp. 1200-1209
Author(s):  
Janina R. Heldt
Keyword(s):  
Mirror Symmetry ◽  
Energy Levels ◽  
Bathochromic Shift ◽  
Heavy Atom ◽  
Excited State Absorption ◽  
Spectroscopic Properties ◽  
Quantum Yields ◽  
Fluorescence Quantum Yields ◽  
Ring Molecules ◽  
Meso Position

The ground-(S0) and excited -(S1 and T1) state spectra of seven derivatives o f 9-acetoxy- 10(4´-acetoxy)phenylanthracene were determined in the region 50000 - 15000 cm -1 (200 - 660 nm). Comparison of these spectra to the unsubstituted molecule (anthracene) indicates the presence o f bathochromic shift and the steric effect. The substituents cause changes of positions of the energy levels (bigger shifts are noticed for low lying states) and also changes of the absorption intensities of some transitions. The steric hindrances between the phenyl-substituents and the anthracene skeleton are more pronounced if the - OAc(- Me) group or a heavy atom is introduced at position 2´o f the phenyl ring. Molecules possessing such substituents at the meso-position exhibit spectroscopic properties characteristic for a plane molecule in the S0 and S1 states; they show a better preservation of the mirror symmetry between the absorption and fluorescence spectra, lower Stokes shifts and the destabilization energies and bigger fluorescence quantum yields.

scholarly journals Ionic State Relaxation Processes in VUV-Excited Polyatomic Molecules

1983 ◽  
Vol 2 (5-6) ◽  
pp. 285-307 ◽  
Author(s):  
Sydney Leach ◽  
Gérald Dujardin
Keyword(s):  
Vibrational Energy ◽  
Molecular Ions ◽  
Quantum Yields ◽  
Relaxation Processes ◽  
Relaxation Rates ◽  
Model Calculations ◽  
Relaxation Parameters ◽  
Gradual Onset ◽  
Mode Selectivity ◽  
Vibrational Levels

Advantages of molecular ions for the study of electronic radiationless transitions are discussed. Several coincidence techniques for measuring key relaxation parameters are briefly described. The different cases of radiationless transition studies of molecular ions are outlined and examples mentioned. Coincidence measurements between threshold photoelectrons and ion fluorescence photons emitted by VUV-excited hexafluorobenzene are presented. The radiative, kr, and nonradiative, knr, relaxation rates for specific vibrational levels in the B∼2A2u and C∼2B2u states of C6F6+ are derived from the measured lifetimes and quantum yields of ion fluorescence. The kr rate for excitation of the C∼, 0° level is found to be about 25% of that for the B∼2A2u state where kr = (18±3) × 106 s−1. The knr rates for the 1n and 1n21 progressions in the B∼ state increase with n but exhibit a mode selective behavior. Model calculations of knr confirm the mode selectivity. These calculations were carried out on a noncommunicating, harmonic oscillator basis. Progressive deviations between experimental and calculated results are interpreted as indicating the gradual onset of vibrational redistribution with increasing vibrational energy. The results illustrate a new method for demonstrating the growing in of intramolecular vibrational relaxation.

meso-(2-Benzimidazolyl)-substituted BODIPYs: Synthesis, structures and spectroscopic properties

2020 ◽  
Vol 24 (01n03) ◽  
pp. 230-237
Author(s):  
Hu Gao ◽  
Chenhong Li ◽  
Zhen Shen
Keyword(s):  
Quantum Yield ◽  
Spectroscopic Properties ◽  
Crystallographic Analysis ◽  
Membered Ring ◽  
Quantum Yields ◽  
Fluorescence Quantum Yields ◽  
Nir Dyes ◽  
Nir Fluorescence ◽  
Yield Formula ◽  
Post Modification

A series of meso-(2-benzimidazolyl)-substituted boron dipyrromethene (BODIPY) derivatives 3a–3c and 4 have been synthesized and characterized. The absorption and fluorescence bands of 3a are bathochromically shifted by 36 nm and 61 nm, respectively, compared with those of the meso-phenyl BODIPY in toluene. More importantly, the fluorescence quantum yields of these meso-(2-benzimidazolyl)-substituted BODIPYs (up to 0.45 in toluene) are much higher than those of the previously reported meso-heterocyclic BODIPYs. X-ray crystallographic analysis of the single crystal structure of 3a revealed that the dihedral angle of meso-benzimidazolyl ring and indacene plane (40.47[Formula: see text] ) is smaller compared with that of the meso-tolyl substituted BODIPY (61.4[Formula: see text] ). Replacement of the six-membered ring with a five-membered ring, as well as the absence of hydrogen at the imino-nitrogen, generated the reduced repulsion and the hydrogen bonding interaction. The increased planarity not only provided the substantial delocalization of [Formula: see text] electrons and red shifted the absorption and emission bands but also enhanced the fluorescence quantum yield by reducing free rotation induced nonradiative deactivation pathway. Furthermore, 3,5-distyryl coupled BODIPY 4 exhibits a NIR fluorescence band at 712 nm with moderate quantum yield ([Formula: see text] [Formula: see text] 0.3) in nonpolar and polar solvents, which indicate that meso-(2-benzimidazolyl) BODIPY acts as a good candidate for post modification toward NIR dyes for biological applications.

scholarly journals Synthesis and properties of 5,10,15,20-tetra[4-(3,5-dioctoxybenzamidephenyl] porphyrin and its metal complexes

2012 ◽  
Vol 77 (3) ◽  
pp. 335-348 ◽  
Author(s):  
Wenhui Lian ◽  
Yuanyuan Sun ◽  
Binbin Wang ◽  
Ning Shan ◽  
Tongshun Shi
Keyword(s):  
Metal Complexes ◽  
Raman Spectra ◽  
Metal Ion ◽  
Spectroscopic Properties ◽  
Molecular Structures ◽  
Photoelectron Spectra ◽  
Quantum Yields ◽  
Xps Spectra ◽  
Fluorescence Quantum Yields ◽  
Porphyrin Ligand

A novel 5,10,15,20-tetra[4-(3,5-dioctoxybenzamide)phenyl]porphyrin and its transition metal complexes are reported in this paper. Their molecular structures were characterized by elemental analysis, IR spectra, 1HNMR spectra and UV-Vis spectra. Their spectroscopic properties were studied by Raman spectra, fluorescence spectra and X-ray photoelectron spectra (XPS). The fluorescence quantum yields have been measured at room temperature. The fluorescence intensity of porphyrin ligand was stronger than that of the complexes. In Raman spectra, there was much difference between porphyrin ligand and its metal complexes due to changes of the symmetry of porphyrin plane. In the XPS spectra, the replacement of the free-base protons by a metal ion to form the metalloporphyrin increases the symmetry of the molecule also introduces an electron with-drawing group into the center of the porphyrin ligand which increases the N1s binding energy.

scholarly journals The Effect of Varying Short-Chain Alkyl Substitution on the Molar Absorptivity and Quantum Yield of Cyanine Dyes

2011 ◽  
Vol 6 ◽  
pp. ACI.S6568 ◽  
Author(s):  
Gala Chapman ◽  
Maged Henary ◽  
Gabor Patonay
Keyword(s):  
Quantum Yield ◽  
Alkyl Chain ◽  
Cyanine Dyes ◽  
Spectroscopic Properties ◽  
Molar Absorptivity ◽  
Alkyl Chain Length ◽  
Short Chain ◽  
Quantum Yields ◽  
Fluorescence Quantum Yields ◽  
Alkyl Substitution

The effect of varying short-chain alkyl substitution of the indole nitrogens on the spectroscopic properties of cyanine dyes was examined. Molar absorptivities and fluorescence quantum yields were determined for a set of pentamethine dyes and a set of heptamethine dyes for which the substitution of the indole nitrogen was varied. For both sets of dyes, increasing alkyl chain length resulted in no significant change in quantum yield or molar absorptivity. These results may be useful in designing new cyanine dyes for analytical applications and predicting their spectroscopic properties.

Influence of Internal Heavy Atoms on the Spectroscopic Properties of 9-Acetoxy-10-Phenylanthracene Derivatives

1984 ◽  
Vol 39 (10) ◽  
pp. 952-959 ◽  
Author(s):  
Janina R. Heidt
Keyword(s):  
Mirror Symmetry ◽  
Fluorescence Spectra ◽  
Spectroscopic Properties ◽  
Quantum Yields ◽  
Absorption And Fluorescence Spectra ◽  
Fluorescence Quantum Yields ◽  
Heavy Atoms ◽  
Decay Times ◽  
Anthracene Derivatives ◽  
Derivatives Of

Abstract Absorption and fluorescence spectra, fluorescence quantum yields and decay times have been measured for new derivatives of 9-acetoxy-10-acetoxyhalogenophenylanthracene in dioxane. It is found that the strength of the absorption transition decreases with increases atomic number Z of the halogen substituent whereas the strength of the fluorescence transition is constant with the exception for the fluoro-substituted derivatives. The loss of mirror symmetry between the absorption and fluorescence spectra is more evident for the 10-(4-acetoxy-3'-halogenophenyl)anthracene derivatives than for the remaining compounds. The determined nonradiative electronic relaxation rate constant and "dark reactions" quantum yield increases with increasing Z value. These findings are explained on the basis of the spin-orbit coupling enlarged by the heavy substituent and through perturbation of the functional groups, which causes different changes of the molecular geometries in the S0 and S*1 states, respectively.

Regioselective Oxidative Cross-Coupling Reaction: Synthesis of Imidazo[1,2-a]pyridine Fluorophores

Synthesis ◽  
2021 ◽  
Author(s):  
Xianglong Chu ◽  
Yadi Niu ◽  
Chen Ma ◽  
Xiaodong Wang ◽  
Yunliang Lin ◽  
...  
Keyword(s):  
Photophysical Properties ◽  
Coupling Reaction ◽  
Cross Coupling ◽  
Quantum Yields ◽  
Fluorescence Quantum Yields ◽  
Cross Coupling Reaction ◽  
Color Tunable ◽  
Palladium Catalyzed ◽  
Structure Relationship ◽  
High Fluorescence

AbstractA rapid access to a series of N-heteroarene fluorophores has been developed on the basis of the palladium-catalyzed direct oxidative C–H/C–H coupling of imidazo[1,2-a]pyridines with thiophenes/furans. The photophysical properties–structure relationship was systematically investigated. The resulting N-heteroarene fluorophores present color-tunable emissions (λem: 431–507 nm in CH2Cl2) and high fluorescence quantum yields (up to 91% in CH2Cl2).

scholarly journals Indenopyrans – synthesis and photoluminescence properties

2016 ◽  
Vol 12 ◽  
pp. 825-834 ◽  
Author(s):  
Andreea Petronela Diac ◽  
Ana-Maria Ţepeş ◽  
Albert Soran ◽  
Ion Grosu ◽  
Anamaria Terec ◽  
...  
Keyword(s):  
Solid State ◽  
Emission Band ◽  
Fluorescence Spectra ◽  
Photophysical Properties ◽  
Quantum Yields ◽  
Band Broadening ◽  
Photoluminescence Properties ◽  
Fluorescence Quantum Yields ◽  
Blue Emitters ◽  
Solid State Fluorescence

New indeno[1,2-c]pyran-3-ones bearing different substituents at the pyran moiety were synthesized and their photophysical properties were investigated. In solution all compounds were found to be blue emitters and the trans isomers exhibited significantly higher fluorescence quantum yields (relative to 9,10-diphenylanthracene) as compared to the corresponding cis isomers. The solid-state fluorescence spectra revealed an important red shift of λmax due to intermolecular interactions in the lattice, along with an emission-band broadening, as compared to the solution fluorescence spectra.

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