Optical absorption and emission properties of fluoranthene, benzo[k]fluoranthene, and their derivatives. A DFT study

Investigation of the Interaction of Benzo(a)Pyrene and Fluoranthene with Cucurbit[n]urils (n = 6-8): Experimental and Molecular Dynamic Study

The inclusion complexes of cucurbit[n]uril, CB[n] (n = 6-8), with poly aromatic hydrocarbon (PAH) Benzo(a)Pyrene (BaP), and fluoranthene (FLT) were investigated carefully in aqueous media. Fluorescence and ¹H NMR spectroscopy were used to characterize and investigate the inclusion complexes that were prepared in the aqueous media. The most predominant complexes of both guests with hosts were the 1:1 guest: host complexes. Stability constants of 2322 ± 547 M^-1, 7281 ± 689 M^-1, 3566 ± 473 M^-1 were obtained for the complexes of BaP with CB[6], CB[7], and CB[8], respectively. On the other hand, stability constants of 5900.270 ± 326 M^-1, 726.87 ± 78 M^-1, 3327.059 ± 153 M^-1 were obtained for the complexes of FLT with CB[6], CB[7], and CB[8], respectively. Molecular dynamic (MD) simulations were used to study the mode and mechanism of the inclusion process and to monitor the stability of these complexes in aqueous media at an atomistic level. Analysis of MD trajectories has shown that both BaP and FLT form stable inclusion complexes with CB[7] and CB[8] in aqueous media throughout the simulation time, subsequently corroborating the experimental results. Nevertheless, the small size of CB[6] prohibited the encapsulation of the two PAHs inside the cavity, but stable exclusion complex was observed between them. The main driving forces for the stability of these complexes are the hydrophobic forces, van der Waals interactions, electrostatic effect, the π····π and C-H···π interaction. These results suggest that BaP and FLT can form stable complexes with CB[n] (n = 6-8) in solution.

True molecular conformation and structure determination by three-dimensional electron diffraction of PAH by-products potentially useful for electronic applications

The true molecular conformation and the crystal structure of benzo[e]dinaphtho[2,3-a;1',2',3',4'-ghi]fluoranthene, 7,14-diphenylnaphtho[1,2,3,4-cde]bisanthene and 7,16-diphenylnaphtho[1,2,3,4-cde]helianthrene were determined ab initio by 3D electron diffraction. All three molecules are remarkable polycyclic aromatic hydrocarbons. The molecular conformation of two of these compounds could not be determined via classical spectroscopic methods due to the large size of the molecule and the occurrence of multiple and reciprocally connected aromatic rings. The molecular structure of the third molecule was previously considered provisional. These compounds were isolated as by-products in the synthesis of similar products and were at the same time nanocrystalline and available only in very limited amounts. 3D electron diffraction data, taken from submicrometric single crystals, allowed for direct ab initio structure solution and the unbiased determination of the internal molecular conformation. Detailed synthetic routes and spectroscopic analyses are also discussed. Based on many-body perturbation theory simulations, benzo[e]dinaphtho[2,3-a;1',2',3',4'-ghi]fluoranthene may be a promising candidate for triplet-triplet annihilation and 7,14-diphenylnaphtho[1,2,3,4-cde]bisanthene may be a promising candidate for intermolecular singlet fission in the solid state.

Fluoranthene dyes for the detection of water content in methanol

Three novel fluoranthene dyes were obtained by cycloaddition reactions using acrylonitrile and dialkyl acetylenedicarboxylates. Their fluorescence properties in different polar-organic solvents were investigated systematically. Meanwhile, spectral changes induced by the addition of water in methanol were observed, indicating that these fluoranthenes dyes can be efficiently used to detect the water content in methanol as probes. Significantly, the practical test measurements for the water contents in methanol illustrated the measured results with the three fluorescent probes were basically consistent with the water content added artificially. This demonstrated the potential of these fluoranthene dyes as probes in measuring the water content in methanol.

Synthesis of 7,12-bis(4-(di(1H-pyrrol-2-yl)methyl)phenyl)benzo[k]fluoranthene from a new dialdehyde as a novel fluorometric bis-Dipyrromethane derivative

Dipyrromethanes are useful mediator structures which can be used as a part of other molecules such as bis-porphyrins and their derivations. Various methods have been developed for their synthesis. This study presents the synthesis of a new bis-dipyrromethane, 7,12-bis(4-(di(1H-pyrrol-2-yl)methyl)phenyl)benzo[k]fluoranthene, using the Lewis acid catalyzed reaction between a new dialdehyde and pyrrole at room temperature. The UV spectroscopic and fluorometric properties of the final product and precursors were determined. The newly synthesized product with desirable UV spectroscopic and fluorometric properties has the potential to be applied as a part of bis-porphyrins or it can be used for other purposes in future studies.

The development of a highly selective fluorescent probe for the rapid detection of HClO in living cells and zebrafish

A new turn-on fluorescent probe, BM-HA, for the rapid detection of HClO in living cells and zebrafish is proposed, and DFT/TDDFT calculations provide insights into the optical properties of the BM-HA probe.

Characterizing the bacterial consortium ASDF capable of catabolic degradation of fluoranthene and other mono- and poly-aromatic hydrocarbons

In this study, a bacterial consortium ASDF was developed, capable of degrading fluoranthene (a non-alternant poly-aromatic hydrocarbon). It comprised of three bacterial strains: Pseudomonas sp. ASDF1, Burkholderia sp. ASDF2 and Mycobacterium sp. ASDF3 capable of degrading 100 mg/L of fluoranthene under experimentally defined and optimum conditions (37 °C, pH 7.0, 150 rpm) within 7 days. Consortium had metabolized fluoranthene as sole source of carbon and energy with maximum degradation rate of 0.52 mg/L/h and growth rate of 0.054/h. Fluoranthene degradation is an aerobic process, therefore with increasing the gyratory shaking from 50 to 150 rpm, degradation was concurrently enhanced by 7.1-fold. The synthetic surfactants SDS and CTAB had antagonistic effect on fluoranthene degradation (decreased up to 2.8-fold). The proficiency of consortium was assessed for its inherent ability to degrade seven other hydrocarbons both individually as well as in mixture. The degradation profile was studied using HPLC and the detection of two degraded intermediates (salicylic acid and derivatives of phthalic acid) suggested that fluoranthene degradation might have occurred via ortho- and meta-cleavage pathways. The competency of consortium was further validated through simulated microcosm studies, which showed 96% degradation of fluoranthene in soil ecosystem under the ambient conditions. Hence, the study suggested that the consortium ASDF has an inherent potential for its wide applicability in bioremediation of hydrocarbon-contaminated sites.

Understanding charge carrier dynamics in a P3HT:FLR blend

In organic semiconductors, optical absorption is pivotal for the performance of optoelectronic devices. The absorption by the semiconductors generates excitons which dissociate into free charge carriers, resulting in energy conversion. Although high performance has been achieved in non-fullerene organic solar cells, their charge generation behavior is far from being well understood. Keeping this in view, we have employed optical spectroscopic tools to study the charge generation mechanism in FLR (1,6,7,10-tetramethylfluoranthene) as a non-fullerene electron acceptor blended with P3HT (poly(3-hexylthiophene)) as an electron donor in five different solvents. Through steady state UV-visible and photoluminescence spectroscopy, we provide a basic understanding of charge transport by enlightening the influence of solvents on the aggregation behavior and exciton bandwidth. Furthermore, for the first time, by employing ultrafast vis-NIR transient absorption spectroscopy, we address the ultrafast charge generation and charge separation mechanism with systematic variation in solvent polarity by incorporating the time evolution of the transient species under various pump-probe wavelengths in the range of 450 nm to 1600 nm. For the different excitation wavelengths, the lifetime kinetics have been depicted by their multiexponential fits. The results show a fast decay term at a lifetime of a few picoseconds (ps) (∼1 to 5 ps) and a slow decay term at a lifetime of ∼500 ps. The charge generation in the P3HT:FLR blend proceeds on a ps time scale, which implies good intermixing of the components. It is clearly established that the non-halogenated solvents influence this aggregation behavior and higher conjugation lengths with higher photoluminescence quenching contribute to the higher charge generation. The enhanced polaron population in P3HT with the addition of FLR illustrates the importance of this acceptor material in the blend because a good solvent-material combination is essential to enhance the charge generation. As such, this comprehensive study explicitly shows the role of FLR as an emerging efficient non-fullerene acceptor for further improving the performance of devices.

NLOphoric Triphenylamine Derived Donor-π-Acceptor-π-Donor Based Colorants: Synthesis, Spectroscopic, Density Functional Theory and Z-scan Studies

Three Donor-π-Acceptor-π-Donor type styryl dyes (5a-c) with different secondary donors are synthesized and characterized to study their nonlinear and linear optical properties. The structure-property relationships of the dyes are described in the light of systematic photophysical and theoretical investigations. The photophysical characteristics of 5a-c are influenced by the polarity of the medium, with an appreciable bathochromic shift in emission (5b = 81 nm) and large Stoke shifts (5b = 104-173 nm) in polar solvents. 5a-c showed intramolecular charge transfer characteristics recognized with the help of emission solvatochromism, solvent polarity graphs, natural bond orbital analysis and HOMO-LUMO energy difference. The optimized geometry and frontier molecular orbitals reveal that the electron donation takes place from secondary donors and not from a fixed donor (triphenylamine) which is more twisted. The nonlinear optical properties obtained using solvent induced spectral shift and computational methods are found within the limiting values. Z-scan results reveal saturable kind of behavior for 5a, 5b and 5c, whereas 5a and 5b show reverse saturable kind of behavior in acetone and ethanol and hence give optical limiting values. The two-photon absorption cross section described by two-level approximation is highest for 5b (251-300 GM).

Investigation of aromatic hydrocarbon inclusion into cyclodextrins by Raman spectroscopy and thermal analysis

Among various cavitand molecules, cyclodextrins are extensively studied due to their ability to form host-guest complexes with small hydrophobic molecules. Aiming to explore cyclodextrin implementation on the scopes related to the environmental pollution monitoring or remediation, extensive studies for understanding the cyclodextrin-based host-guest complex formation with selected targeted substances are conducted. In this context, two polycyclic aromatic hydrocarbons, naphthalene and fluoranthene as well as toluene as a member of volatile organic compounds, were studied regarding their ability to encapsulate into cyclodextrin cavities. Synthesised complexes were examined by thermogravimetric analysis combined with Raman spectroscopy. The obtained results demonstrated that the size between targeted molecules and the cyclodextrin cavities strongly correlates with its ability to engage in complexation. Thus, this latter parameter plays an important role in the inclusion complex formation as well as in the strength of the interaction between the molecules.

Photo-induced characteristic study of the smallest fullerene fragment, 1,6,7,10-tetramethylfluoranthene as an acceptor

In this study, the use of the novel 1,6,7,10-tetramethylfluoranthene as an acceptor in the organic solar cell has been demonstrated.

Novel Thiazole Based Styryl Dyes with Benzimidazole Unit - Synthesis, Photophysical and TD-DFT Studies

Three new Y-shaped styryl dyes were designed and synthesized from thiazole carbaldehyde with different active methylene compounds as acceptor moieties. All the dyes were characterized by IR, ¹HNMR, MS/LCMS/HRMS. Spectroscopic properties and non-linear optical properties styryl derivatives were analyzed and the effect of change in solvent polarity on their absorption and emissive properties has been investigated. The dye with (1-phenylethylidene) propanedinitrile unit shows red shift absorption/emission profile among all the dyes. Density Functional Theory and Time Dependent-Density Functional Theory computations have been used for comparative study with the experimental data and also to understand the structural, molecular, electronic and photophysical parameters of the styryl dyes. The computational method was also employed to investigate the nonlinear optical properties of the styryl dyes in different organic solvent. The unsubstituted benzimidazolyl thiazole styryl dyes possess good non-linear optical properties.

Rational design of cyclopenta[b]naphthalenes for better optoelectronic applications and their photophysical properties using DFT/TD-DFT methods

The optical properties of cyclopenta[b]naphthalenes (CPNs) can be fine-tuned by suitable substitutions and DFT calculations show that they can make efficient OLEDs.

N-2-Aryl-1,2,3-Triazoles: A Novel Class of Blue Emitting Fluorophores-Synthesis, Photophysical Properties Study and DFT Computations

Novel fluorescent 2-[4-(4,5-diphenyl-1H-imidazol-2-yl) phenyl]-2H-naphtho [1,2-d] [1,2,3] triazolyl derivatives were synthesized from 4-(4,5-diphenyl-1H-imidazol-2-yl) aniline and substituted naphthalen-2-amine. The photophysical properties of the three new fluorophores were evaluated in acetonitrile, methanol, dimethylsulfoxide and N,N-dimethylformamide solvents and were compared with the reported analogs. The compounds show the absorption in the ultraviolet region and the emission in the blue region. The thermal stabilities of these compounds was evaluated by thermogravimetric analysis. The solvatochromism data are used for ground and excited state dipole moment determination of the synthesized triazoles using Bakhshiev and Bilot-Kawski correlations. The experimental absorption and emission were compared with the theoretical data obtained by DFT and TD-DFT computations and they are well in agreement with each other.

Biotransformation of the high-molecular weight polycyclic aromatic hydrocarbon (PAH) benzo[k]fluoranthene by Sphingobium sp. strain KK22 and identification of new products of non-alternant PAH biodegradation by liquid chromatography electrospray ionization tandem mass spectrometry

A pathway for the biotransformation of the environmental pollutant and high-molecular weight polycyclic aromatic hydrocarbon (PAH) benzo[k]fluoranthene by a soil bacterium was constructed through analyses of results from liquid chromatography negative electrospray ionization tandem mass spectrometry (LC/ESI(–)-MS/MS). Exposure of Sphingobium sp. strain KK22 to benzo[k]fluoranthene resulted in transformation to four-, three-and two-aromatic ring products. The structurally similar four-and three-ring non-alternant PAHs fluoranthene and acenaphthylene were also biotransformed by strain KK22, and LC/ESI(–)-MS/MS analyses of these products confirmed the lower biotransformation pathway proposed for benzo[k]fluoranthene. In all, seven products from benzo[k]fluoranthene and seven products from fluoranthene were revealed and included previously unreported products from both PAHs. Benzo[k]fluoranthene biotransformation proceeded through ortho-cleavage of 8,9-dihydroxy-benzo[k]fluoranthene to 8-carboxyfluoranthenyl-9-propenic acid and 9-hydroxy-fluoranthene-8-carboxylic acid, and was followed by meta-cleavage to produce 3-(2-formylacenaphthylen-1-yl)-2-hydroxy-prop-2-enoic acid. The fluoranthene pathway converged with the benzo[k]fluoranthene pathway through detection of the three-ring product, 2-formylacenaphthylene-1-carboxylic acid. Production of key downstream metabolites, 1,8-naphthalic anhydride and 1-naphthoic acid from benzo[k]fluoranthene, fluoranthene and acenaphthylene biotransformations provided evidence for a common pathway by strain KK22 for all three PAHs through acenaphthoquinone. Quantitative analysis of benzo[k]fluoranthene biotransformation by strain KK22 confirmed biodegradation. This is the first pathway proposed for the biotransformation of benzo[k]fluoranthene by a bacterium.