Steric Effects in the Electronic Spectra of the 3,5-Diarylaminobenzene Derivatives

1986 ◽  
Vol 41 (11) ◽  
pp. 1311-1314 ◽  
Author(s):  
A. Balter ◽  
W. Nowak ◽  
P. Milart ◽  
J. Sepioł
Keyword(s):  
Excited State ◽  
Electronic Spectra ◽  
Fluorescence Properties ◽  
Steric Effects ◽  
Quantum Yields ◽  
Spectroscopic Behaviour ◽  
Fluorescence Quantum Yields ◽  
Excited State Lifetimes ◽  
Methyl Phenyl

Absorption and fluorescence properties, excited state lifetimes and fluorescence quantum yields were determined for a series of 3,5-diarylaminobenzene derivatives in solvents of different polarities. The role of the nitrile, methyl, phenyl and naphthyl substituents is discussed. Especially the steric effects on the spectroscopic behaviour of the investigated molecules are studied.

scholarly journals Competition between radiative and nonradiative excited state processes in photoluminescent organic molecular crystals

2020 ◽  
Author(s):  
Miguel Rivera ◽  
Ljiljana Stojanovic ◽  
Rachel Crespo Otero
Keyword(s):  
Excited State ◽  
Molecular Crystals ◽  
State Level ◽  
High Energy ◽  
Quantum Yields ◽  
Conical Intersections ◽  
Fluorescence Quantum Yields ◽  
Exciton Coupling ◽  
Organic Molecular Crystals

<p>Organic molecular crystals are attractive materials for luminescent applications due to their promised tunability. However, the link between chemical structure and emissive behaviour is poorly understood due to the numerous interconnected factors which are at play in determining radiative and non-radiative behaviours at the solid state level. In this study, we investigate thirteen luminescent molecular crystals and apply newly implemented tools to study their geometric properties and constituent dimer excitonic coupling values. We then focus on the excited state decay pathways of five of the molecules. The competition between radiative and nonradiative processes was used to rationalise the different fluorescence quantum yields across systems. We found that due to the prevalence of sheet and herringbone packing in organic molecular crystals, the conformational diversity of crystal dimers is limited. Additionally, similarly spaced dimers have exciton coupling values of similar order within a 50 meV interval. Finally, we found that the accessibility of conical intersection geometries was a robust indicator of the role of nonradiative decay in the excited state mechanism of most molecules. The conical intersections all displayed a measure of rotation and puckering, where purely rotational conical intersections in vacuum lead to high energy puckered conical intersections in the crystal phase.</p>

scholarly journals Mono- Versus Bicyclic Carbene Metal Amide Photoemitters: Which Design Leads to Best Performance?

2020 ◽  
Author(s):  
Florian Chotard ◽  
Vasily Sivchik ◽  
Mikko Linnolahti ◽  
Manfred Bochmann ◽  
Alexander Romanov
Keyword(s):  
Excited State ◽  
State Energy ◽  
Conformational Flexibility ◽  
Quantum Yields ◽  
Carbene Ligands ◽  
Lumo Energy ◽  
Excited State Energy ◽  
Excited State Lifetimes

New luminescent “carbene-metal-amide” (CMA) Cu, Ag and Au complexes based on monocyclic (C6) or bicyclic six-ring (BIC6) cyclic (alkyl)(amino)carbene ligands illustrates the effects of LUMO energy stabilization, conformational flexibility and excited state energy on the photoemission properties, leading to near-quantitative quantum yields, short excited state lifetimes Cu > Au > Ag down to 0.5 µs and high radiative rates of 10<sup>6</sup> s<sup>–1</sup>.

scholarly journals Photoluminescence in m-carborane–anthracene triads: a combined experimental and computational study

2018 ◽  
Vol 6 (42) ◽  
pp. 11336-11347 ◽  
Author(s):  
Mahdi Chaari ◽  
Zsolt Kelemen ◽  
José Giner Planas ◽  
Francesc Teixidor ◽  
Duane Choquesillo-Lazarte ◽  
...  
Keyword(s):  
Computational Study ◽  
Fluorescence Emission ◽  
Fluorescence Properties ◽  
Quantum Yields ◽  
Aggregate State ◽  
Fluorescence Quantum Yields ◽  
High Fluorescence

m-Carborane has demonstrated to be a perfect platform to boost the fluorescence properties of anthracene, giving rise to high fluorescence quantum yields in solution and also retaining fluorescence emission in the aggregate state.

Excited state acid–base equilibrium of tyrosine

1978 ◽  
Vol 56 (9) ◽  
pp. 1238-1245 ◽  
Author(s):  
David Michael Rayner ◽  
Donald Theodore Krajcarski ◽  
Arthur Gustav Szabo
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Quantum Yields ◽  
Acid Base ◽  
Large Shift ◽  
Fluorescence Quantum Yields ◽  
Base Equilibrium ◽  
Tyrosine Fluorescence ◽  
Acid Base Equilibrium ◽  
Buffer Base

Fluorescence attributable to the tyrosinate form of the amino acid tyrosine, previously only observed at pH > pK(S0) = 10.3 where tyrosinate exists in the ground state, has been observed at neutral pH in the presence of high buffer base concentrations. This observation is consistent with the large shift in pK(Sl) predicted from absorption measurements and confirms that proton transfer is indeed a mechanism by which carboxylate ions quench tyrosine fluorescence. The dependence of the fluorescence quantum yields of tyrosine and tyrosinate on pH does not fit a simple excited state acid–base equilibrium model but a more complicated system where carboxylate is also capable of simultaneously quenching tyrosine fluorescence by a mechanism not involving proton transfer. Kinetic analysis of the system allows calculation of pK(S1) = 4.2 for tyrosine. The quantum yield of tyrosinate fluorescence can be appreciably higher than that normally measured at alkaline pH where a separate quenching mechanism must operate. These results have significance in the interpretation of the fluorescence properties of proteins.

Synthesis, characterization and fluorescence properties study of meso-tetrakis(1-arylpyrazole-4-yl)porphyrins

2005 ◽  
Vol 09 (06) ◽  
pp. 430-435 ◽  
Author(s):  
Can-Cheng Guo ◽  
Tie-Gang Ren ◽  
Jian Wang ◽  
Chun-Yan Li ◽  
Jian-Xin Song
Keyword(s):  
Elemental Analysis ◽  
Mass Spectra ◽  
Fluorescence Spectra ◽  
Fluorescence Emission ◽  
Red Shift ◽  
Fluorescence Properties ◽  
Quantum Yields ◽  
Fluorescence Quantum Yields ◽  
H Nmr ◽  
Reaction Condition

Five new meso-tetrakis(1-arylpyrazol-4-yl)porphyrins were synthesized to investigate their fluorescence properties. Preparation of these porphyrins was carried out by cyclization of tetramethoxypropane with substituted phenylhydrazine, followed by formylation to give the corresponding aldehydes, which reacted with pyrrole under the Adler reaction condition to get the target porphyrins (1a-1e). All the porphyrins were characterized by 1 H NMR, elemental analysis, UV-vis spectra and mass spectra. Red fluorescence emission of these porphyrins was observed in fluorescence spectra. Compared with meso-tetraphenylporphyrin (TPPH2), these meso-tetrakis(1-arylpyrazol-4-yl) porphyrins had a significant red shift in UV-vis and fluorescence spectra with increased fluorescence quantum yields.

The influence of phenylethynyl linkers on the photo-physical properties of metal-free porphyrins

2000 ◽  
Vol 04 (07) ◽  
pp. 669-683 ◽  
Author(s):  
GARY A. BAKER ◽  
FRANK V. BRIGHT ◽  
MICHAEL R. DETTY ◽  
SIDDHARTH PANDEY ◽  
COREY E. STILTS ◽  
...  
Keyword(s):  
Excited State ◽  
Radiative Decay ◽  
Phenyl Group ◽  
Quantum Yields ◽  
Fluorescence Lifetimes ◽  
Strongly Coupled ◽  
Metal Free ◽  
Fluorescence Quantum Yields ◽  
Porphyrin Core ◽  
Absorbance Spectra

Series of 5,10,15,20-tetraarylporphyrins 1 and 5,10,15,20-tetrakis[4-(arylethynyl)phenyl]porphyrins 2 were prepared via condensation of pyrrole with the appropriate benzaldehyde or 4-(arylethynyl)benzaldehyde derivative (3). Condensation of meso-phenyldipyrromethane with mixtures of benzaldehyde and 4-(trimethylsilyl-ethynyl)benzaldehyde gave a separable mixture of mono- (6), bis- (both cis-7 and trans-8) and tris[4-(trimethylsilylethynyl)phenyl]porphyrin (9). Following removal of the trimethylsilyl groups of 6–9, the 4-ethynylphenyl groups of 11–14 were coupled to 1-iodo-3,5-di(trifluoromethyl)benzene with Pd ( OAc )2 to give 15–18 bearing one, two (both cis- and trans-) and three 4-[bis-3,5-(trifluoromethyl)phenylethynyl]phenyl groups respectively. Coupling of 11 and 1-iodo-4-nitrobenzene with Pd ( OAc )2 gave porphyrin 19 with one 4-(4-nitrophenylethynyl)phenyl group. Porphyrin 24 with a p-quinone linked to the porphyrin core via a phenylethynyl group was prepared via similar chemistry. The absorbance spectra, emission maxima, excited-state fluorescence lifetimes, quantum yields of fluorescence, rates of fluorescence and rates of non-radiative decay were measured for each of the porphyrins. Absorbance spectra and emission maxima were nearly identical for all the porphyrins of this study, which suggests that the aryl groups and 4-(arylethynyl)phenyl groups are not strongly coupled to the porphyrin core in these metal-free compounds. Fluorescence quantum yields and rates of radiative decay were larger for porphyrins bearing 4-(arylethynyl)phenyl groups, while excited-state fluorescence lifetimes were somewhat shorter. These effects were additive for each additional 4-(arylethynyl)phenyl group.

Energetic basis of excited-state enzyme design and function

2021 ◽  
Author(s):  
Chi-Yun Lin ◽  
Matthew Romei ◽  
Irimpan Mathews ◽  
Steven Boxer
Keyword(s):  
Excited State ◽  
Protein Function ◽  
Fluorescent Protein ◽  
De Novo ◽  
Fitness Landscape ◽  
Quantitative Model ◽  
Efficient Solutions ◽  
Catalyst Design ◽  
Quantum Yields ◽  
Fluorescence Quantum Yields

The last decades have witnessed an explosion of de novo protein designs with a remarkable range of scaffolds. It remains challenging, however, to design catalytic functions that are competitive with naturally occurring counterparts as well as biomimetic or non-biological catalysts. Although directed evolution often offers efficient solutions, the fitness landscape remains opaque. Green fluorescent protein (GFP), which has revolutionized biological imaging and assays, is one of the most re-designed proteins. While not an enzyme in the conventional sense, GFPs feature competing excited-state decay pathways with the same steric and electrostatic origins as conventional ground-state catalysts, and they exert exquisite control over multiple reaction outcomes through the same principles. Thus, GFP is an “excited-state enzyme”. Herein we show that rationally designed mutants and hybrids that contain environmental mutations and substituted chromophores provide the basis for a quantitative model and prediction that describes the influence of sterics and electrostatics on excited-state catalysis of GFPs. As both perturbations can selectively bias photoisomerization pathways, GFPs with fluorescence quantum yields (FQYs) and photoswitching characteristics tailored for specific applications could be predicted and then demonstrated. The underlying energetic landscape, readily accessible via spectroscopy for GFPs, offers an important missing link in the design of protein function that is generalizable to catalyst design.

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