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Journal ArticleDOI

Reinterpretation of the anomalous fluorescense of p-n,n-dimethylamino-benzonitrile

01 Apr 1973-Chemical Physics Letters (North-Holland)-Vol. 19, Iss: 3, pp 315-318
TL;DR: In this paper, the existence of two excited species differing in polarity and in the orientation of the N(CH 3 ) 2 group has been attributed to the presence of an excimer.
About: This article is published in Chemical Physics Letters.The article was published on 1973-04-01. It has received 724 citations till now. The article focuses on the topics: Lone pair.
Citations
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Journal ArticleDOI
TL;DR: The Rehybridization of the Acceptor (RICT) and Planarization ofThe Molecule (PICT) III is presented, with a comparison of the effects on yield and radiationless deactivation processes.
Abstract: 6. Rehybridization of the Acceptor (RICT) 3908 7. Planarization of the Molecule (PICT) 3909 III. Fluorescence Spectroscopy 3909 A. Solvent Effects and the Model Compounds 3909 1. Solvent Effects on the Spectra 3909 2. Steric Effects and Model Compounds 3911 3. Bandwidths 3913 4. Isoemissive Points 3914 B. Dipole Moments 3915 C. Radiative Rates and Transition Moments 3916 1. Quantum Yields and Radiationless Deactivation Processes 3916

2,924 citations

Journal ArticleDOI
TL;DR: New fluorescent sensing mechanisms that have emerged in the past five years, such as aggregation-induced emission (AIE) and C=N isomerization, which can be ascribed to fluorescence changes via conformational restriction are focused on.
Abstract: During the past decade, fluorescent chemosensors have become an important research field of supramolecular chemistry and have attracted great attention because of their simplicity, high selectivity and sensitivity in fluorescent assays. In the design of new fluorescent chemosensors, exploration of new sensing mechanisms between recognition and signal reporting units is of continuing interest. Based on different photophysical processes, conventional sensing mechanisms including photo-induced electron transfer (PET), intramolecular charge transfer (ICT), metal–ligand charge transfer (MLCT), twisted intramolecular charge transfer (TICT), electronic energy transfer (EET), fluorescence resonance energy transfer (FRET), and excimer/exciplex formation have been investigated and reviewed extensively in the literature. This tutorial review will mainly focus on new fluorescent sensing mechanisms that have emerged in the past five years, such as aggregation-induced emission (AIE) and CN isomerization, which can be ascribed to fluorescence changes via conformational restriction. In addition, excited-state intramolecular proton transfer (ESIPT) has not been well reviewed yet, although a number of chemosensors based on the ESIPT mechanism have been reported. Thus, ESIPT-based chemosensors have been also summarized in this review.

1,511 citations

Journal ArticleDOI
TL;DR: PCM-TDDFT is shown to be successful in supporting the analysis of experimental data with useful insights for a better understanding of photophysical and photochemical pathways in solution.
Abstract: In this paper we present the theory and implementation of analytic derivatives of time-dependent density functional theory (TDDFT) excited states energies, both in vacuo and including solvent effects by means of the polarizable continuum model. The method is applied to two case studies: p-nitroaniline and 4-(dimethyl)aminobenzonitrile. For both molecules PCM-TDDFT is shown to be successful in supporting the analysis of experimental data with useful insights for a better understanding of photophysical and photochemical pathways in solution.

1,160 citations

Journal ArticleDOI
TL;DR: The dual fluorescence of certain aromatic systems has greatly advanced in recent years, and the accompanying large charge separation has been linked to a twisted (or small overlap) arrangement of the chromophores as mentioned in this paper.
Abstract: The understanding of the dual fluorescence of certain aromatic systems has greatly advanced in recent years. The accompanying large charge separation has been shown to be linked to a twisted (or small overlap) arrangement of the chromophores. Recent theoretical models are able to describe the excited-state twisting of both single bonds (TICT compounds) and double bonds (olefins) in a unified picture. These models can help to elucidate the photophysical behavior of many organic, inorganic, and biologically relevant compounds, and their application to laser dyes and fluorescent probes provides a route to new “tailor-made” fluorescent materials. Applied to the primary processes of vision and photosynthesis, these models can lead to a deeper understanding of basic photobiological processes.

1,146 citations

Journal ArticleDOI
TL;DR: With knowledge of the mechanisms of these processes, desired rates and directions can be achieved, and thus the multiple emission spectral features can be harnessed.
Abstract: Charge and proton transfer reactions in the excited states of organic dyes can be coupled in many different ways. Despite the complementarity of charges, they can occur on different time scales and in different directions of the molecular framework. In certain cases, excited-state equilibrium can be established between the charge-transfer and proton-transfer species. The interplay of these reactions can be modulated and even reversed by variations in dye molecular structures and changes of the surrounding media. With knowledge of the mechanisms of these processes, desired rates and directions can be achieved, and thus the multiple emission spectral features can be harnessed. These features have found versatile applications in a number of cutting-edge technological areas, particularly in fluorescence sensing and imaging.

569 citations

References
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Journal ArticleDOI
TL;DR: In this paper, the classification of π-orbitals in a cata-condensed aromatic system is like that of the orbitals of a free electron traveling in a one-dimensional loop of constant potential around the perimeter.
Abstract: The classification of π‐orbitals in a cata‐condensed aromatic system is like that of the orbitals of a free electron traveling in a one‐dimensional loop of constant potential around the perimeter. To take into account electron interaction, certain quantities corresponding to angular momenta may be added or subtracted. Introduction of the cross‐links in the molecule removes the degeneracy. The first excited configuration in such systems gives two low frequency singlet weak absorption bands and two higher singlet strong dipole absorption bands. Selection and polarization rules are given. The levels are identified from the spectra and some of their properties are determined. An explanation is given of the regularities found by Klevens and Platt. A systematic nomenclature is given. The results agree qualitatively with LCAO theory, can be applied easily to unsymmetrical molecules, and can possibly be extended to other types of ring systems.

1,206 citations

Journal ArticleDOI
TL;DR: The Reaktionsmechanismen der strahlungslosen Desaktivierung von Molekeln in angeregten Elektronenzustanden and die zugrundeliegenden Prinzipien werden am Beispiel neuerer fluoreszenzspektroskopischer Ergebnisse an Losungen aromatischer Verbindungen (Merocyanine, Stickstoff-Heterocyclen, Saureamide usw.) dargestellt and erlaut
Abstract: Die Reaktionsmechanismen der strahlungslosen Desaktivierung von Molekeln in angeregten Elektronenzustanden und die zugrundeliegenden Prinzipien werden am Beispiel neuerer fluoreszenzspektroskopischer Ergebnisse an Losungen aromatischer Verbindungen (Merocyanine, Stickstoff-Heterocyclen, Saureamide usw.) dargestellt und erlautert.

438 citations

Journal ArticleDOI
TL;DR: In this paper, un detallado analisisis teorico del elemento matricial spin-orbita-spin for una mezcla singlete-triplete of the promociones 1 a π in anilinas, usando two centros integrados.
Abstract: Resumen El par de electrones aislados del heteroatomo tiene dos orbitales; uno de no union, orbital -n, el cual es del tipo sy es ortogonal con respecto a los orbitales de los electrones; y otro de union orbital l, que esta relacionado con los electrones π, a un grado en que depende del angulo de torsion entre el eje del orbital l y el orbital 2pπ del anillo aromatico vecino. La excitacion de electrones a partir de los orbitales n o l a orbitales de anti-union del tipo π es tratada como una transicion de transferencia de carga int amolecular. Se desarrolla un detallado analisis teorico del elemento matricial orbita-spin para una mezcla singlete-triplete de las promociones 1 a π en anilinas, usando dos centros integrados. El momento de la transicion singlete triplete depende del angulo de torsion entre el eje del orbital 1 y el piano del anillo aromatico. Se provee evidencia experimental para predicir la dependencia angular usando una serie de anilinas restringidas estericamente con distintos angulos de torsion. El reciproco de la vida media de la fosforecencia de estas anilinas tiene una correlacion muy satisfactoria con la funcion teorica, lo cual apoya el uso del elemento matricial spin-orbita.

82 citations

Journal ArticleDOI
TL;DR: In this paper, the absorption and luminescence spectra of N,N-dimethyl-p -cyanoaniline in a variety of solvents are reported.

59 citations