Steric Hindrance and Short Wave Length Bands in the Ultraviolet Spectra of Some Naphthalene and Diphenyl Derivatives<sup>1</sup>

Friedel, R. A.; Orchin, Milton; Reggel, Leslie

doi:10.1021/ja01181a057

Cited by 88 publications

(63 citation statements)

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“…The design principle correctly applies to acene dimers, oligomers and polymers such as A, 37 B, 33 F, 38 G 39 and H, 40 complex geometries such as C,34 I, 41,42 J 43 and K, 44 and to heteroatom-substituted dimers D,35 E,36 and L. 45 R denotes a solubilising or stabilising group. liquid crystals, 41 polymer synthesis, 42 sensors, 45 photovoltaic applications,37,39,43 and one to explore structure-spectrum relationships 32.…”

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confidence: 99%

Anticipating Acene-Based Chromophore Spectra with Molecular Orbital Arguments

et al. 2019

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Recent synthetic studies on the organic molecules tetracene and pentacene have found certain dimers and oligomers to exhibit an intense absorption in the visible region of the spectrum which is not present in the monomer or many previously-studied dimers. In this article we combine experimental synthesis with electronic structure theory and spectral computation to show that this absorption arises from an otherwise dark charge-transfer excitation 'borrowing intensity' from an intense UV excitation.Further, by characterizing the role of relevant monomer molecular orbitals, we arrive at a design principle that allows us to predict the presence or absence of an additional absorption based on the bonding geometry of the dimer. We find this rule correctly explains the spectra of a wide range of acene derivatives and solves an unexplained structure-spectrum phenomenon first observed seventy years ago. These results pave the way for the design of highly absorbent chromophores with applications ranging from photovoltaics to liquid crystals.

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confidence: 99%

Anticipating Acene-Based Chromophore Spectra with Molecular Orbital Arguments

et al. 2019

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“…From our point of view, the data obtained from spirodibenzofluorenes 9 and 34 are quite appealing. Their absorption spectra in CH 2 Cl 2 highly dilute solution feature π→π* transitions at about λ max =353 and 370 nm, showing a large bathochromic shift when compared with the absorption spectra reported for 1,1′‐binaphthyl ( λ max =280 and 295 nm) 42. Interestingly, whereas in typical 2,2′‐binaphthyls there is no conjugation between the two napthyl rings because of the steric repulsions between the substituents at positions 8 and 8′, the geometrical distortion created by the formation of the five‐membered ring enforces a rigid structure in which both naphthyl rings are arranged in a situation closer to planarity, therefore promoting effective conjugation between the rings.…”

Section: Resultsmentioning

confidence: 65%

“…Their absorption spectra in CH 2 Cl 2 highly dilute solutionf eature p!p*t ransitions at about l max = 353 and 370 nm, showingalarge bathochromic shift when compared with the absorption spectra reportedf or 1,1'-binaphthyl (l max = 280 and 295 nm). [42] Interestingly,w hereas in typical 2,2'-binaphthyls there is no conjugation between the two napthyl rings because of the steric repulsionsb etween the substituents at positions 8a nd 8',t he geometrical distortion created by the formation of the fivemembered ring enforces ar igid structure in which both naphthyl rings are arranged in as ituation closer to planarity,t herefore promoting effective conjugation between the rings. In fact, DFT molecular modeling studies predict as tructure in which both naphthalene rings are slightly bent (torsion angle of 21 8)t oa void the steric interaction between the hydrogens at the internal positions (Figure3).…”

Section: Photophysical Propertiesmentioning

confidence: 99%

Structurally Diverse π‐Extended Conjugated Polycarbo‐ and Heterocycles through Pd‐Catalyzed Autotandem Cascades

Barroso

Cabal

Badía‐Laiño

et al. 2015

Chemistry A European J

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The Pd-catalyzed reaction between 2,2'-dibromobiphenyls and related systems with tosylhydrazones gives rise to new π-extended conjugated polycarbo- and heterocycles through an autotandem process involving a cross-coupling reaction followed by an intramolecular Heck cyclization. The reaction shows wide scope regarding both coupling partners. Cyclic and acyclic tosylhydrazones can participate in the process. Additionally, a variety of aromatic and heteroaromatic dibromoderivatives have been employed, leading to an array of diverse scaffolds featuring a fluorene or acridine central nucleus, and containing binaphthyl, thiophene, benzothiophene and indole moieties. The application to appropriate tetrabrominated systems led to greater structural complexity through two consecutive autotandem cascades. The photophysical properties of selected compounds were studied through their absorption and emission spectra. Fluorescence molecules featuring very high quantum yields were identified, showing the potential of this methodology in the development of molecules with interesting optoelectronic properties.

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“…phenanthrene and chrysene). At the same period spectra were taken from naphthalene and biphenyl derivatives [10], m-and o-disubstituted benzene derivatives [11], and mono-substituded and p-disubstituted benzene derivatives [12]. Absorption measurements continued with the same intensity the following decades [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Empirical LCAO parameters forπmolecular orbitals in planar organic molecules

2009

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We present a parametrization within a simplified LCAO model (a type of Hückel model) for the description of π molecular orbitals in organic molecules containing π-bonds between carbon, nitrogen, or oxygen atoms with sp 2 hybridization, which we show to be quite accurate in predicting the energy of the highest occupied π orbital and the first π-π* transition energy for a large set of organic compounds. We provide four empirical parameter values for the diagonal matrix elements of the LCAO description, corresponding to atoms of carbon, nitrogen with one z p electron, nitrogen with two z p electrons, and oxygen. The bond-length dependent formula (proportional to 1/d 2 ) of Harrison is used for the non-diagonal matrix elements between neighboring atoms. The predictions of our calculations have been tested against available experimental results in more than sixty organic molecules, including benzene and its derivatives, polyacenes, aromatic hydrocarbons of various geometries, polyenes, ketones, aldehydes, azabenzenes, nucleic acid bases and others. The comparison is rather successful, taking into account the small number of parameters and the simplicity of the LCAO method, involving only z p atomic orbitals, which leads even to analytical calculations in some cases.Keywords: linear combination of atomic orbitals, Hückel model, empirical parameters, πmolecular structure, highest occupied π orbitals, π-π* transition the assignment of electronic transitions (e.g. singlet-singlet or singlet-triplet transitions, Rydberg transitions, π-π* transitions etc.), and the calculation of the oscillator strength of the transitions. Apart from basic knowledge and the numerous applications of planar organic molecules containing atoms with sp 2 hybridization, the π molecular electronic structure of such compounds is involved in several biological functions. For example, we mention chlorophyll in photosynthesis, the retinal molecule involved in vision or in photondriven ion pumps like bacteriorhodopsin [1], and many molecules with photobiological functions such as vitamin A, vitamin D precursors, carotene etc., containing polyene chromophores [2]. Also new organic semiconductors based in pentacene and other hydrocarbon molecules have attached an enormous interest regarding their use in molecular electronics [3]. Experimental investigations of the electronic structure of organic molecules started very early, by performing absorption measurements. The ultraviolet absorption spectra of eighteen pyridines and purines [4], fourteen ethylenic hydrocarbon molecules [5], and 1,3 cyclohexadiene [6] have been measured already in 30s. Later Platt and Klevens presented the spectra of several alkylbenzenes [7], some ethylenes and acetylenes [8], and seventeen polycyclic aromatic hydrocarbons composed of fused benzene rings [9] (e.g. phenanthrene and chrysene). At the same period spectra were taken from naphthalene and biphenyl derivatives [10], m-and o-disubstituted benzene derivatives [11], and mono-substituded and p-disubstituted benzene derivativ...

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Steric Hindrance and Short Wave Length Bands in the Ultraviolet Spectra of Some Naphthalene and Diphenyl Derivatives¹

Cited by 88 publications

References 0 publications

Anticipating Acene-Based Chromophore Spectra with Molecular Orbital Arguments

Anticipating Acene-Based Chromophore Spectra with Molecular Orbital Arguments

Structurally Diverse π‐Extended Conjugated Polycarbo‐ and Heterocycles through Pd‐Catalyzed Autotandem Cascades

Empirical LCAO parameters forπmolecular orbitals in planar organic molecules

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Steric Hindrance and Short Wave Length Bands in the Ultraviolet Spectra of Some Naphthalene and Diphenyl Derivatives1

Cited by 88 publications

References 0 publications

Anticipating Acene-Based Chromophore Spectra with Molecular Orbital Arguments

Anticipating Acene-Based Chromophore Spectra with Molecular Orbital Arguments

Structurally Diverse π‐Extended Conjugated Polycarbo‐ and Heterocycles through Pd‐Catalyzed Autotandem Cascades

Empirical LCAO parameters forπmolecular orbitals in planar organic molecules

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Product

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Steric Hindrance and Short Wave Length Bands in the Ultraviolet Spectra of Some Naphthalene and Diphenyl Derivatives¹