Synthesis of 1,3-Diphenyl-6-alkyl/aryl-Substituted Fulvene Chromophores: Observation of π–π Interactions in a 6-Pyrene-Substituted 1,3-Diphenylfulvene

Divalent ansa-Octaphenyllanthanocenes: Synthesis, Structures, and EuII Luminescence

Reductive dimerization of fulvenes using low-valent metal precursors is a straightforward one-step approach to access ethylene-bridged metallocenes. This process has so far mainly been employed with fulvenes carrying one or two substituents in the exocyclic position. In this work, a new synthesis of the unsubstituted exocyclic 1,2,3,4-tetraphenylfulvene (1), its full structural characterization by NMR spectroscopy and single-crystal X-ray diffraction, as well as some photophysical properties and its first use in reductive dimerization are described. This fulvene reacted with different lanthanoid metals in thf to provide the divalent ansa-octaphenylmetallocenes [Ln(C5Ph4CH2)2(thf)n] (Ln = Sm, n = 2 (2); Ln = Eu, n = 2 (3); and Ln = Yb, n = 1 (4)). These complexes were characterized by X-ray diffraction, laser desorption/ionization time of flight mass spectrometry, and, in the case of Sm and Yb, multinuclear NMR spectroscopy, showing the influence of the ansa-bridge on solution and solid-state structures compared to previously reported unbridged metallocenes. Furthermore, the luminescence properties of the Eu ansa complex 3 were studied in solution and the solid state, revealing significant differences with the known octa- and deca-phenyleuropocenes, [Eu(C5Ph4H)2(dme)] and [Eu(C5Ph5)2].

Palladium-Catalyzed Synthesis of 3,6-Diaryl-1-silylfulvenes: A Promising Entry for Preparing 1,3,6-Triarylfulvenes Bearing Three Different Aryl Groups

We developed a synthetic methodology for preparing (E)-1,3,6-triarylfulvenes bearing three different aryl groups. The reaction of 1,4-diaryl-1-bromo-1,3-butadienes with silylacetylenes in the presence of a palladium catalyst produced (E)-3,6-diaryl-1-silyl-fulvenes in good to excellent yields. The (isopropoxy)silylated fulvenes thus obtained were converted to (E)-1,3,6-triarylfulvenes bearing different types of aryl substituents. (E)-3,6-Diaryl-1-silyl-fulvenes are promising templates for the synthesis of diverse (E)-1,3,6-triarylfulvenes.

Connect Four: Tetraarylated Dihydropentalenes and Triarylated Monocyclic Pentafulvenes from Cyclopentadienes and Enones

In search of novel pentalenide ligands for use in organometallic chemistry and homogeneous catalysis, we report the scope of a straightforward base-promoted Michael annulation of cyclopentadienes with α,β-unsaturated ketones that allows the introduction of symmetrical as well as unsymmetrical aryl and alkyl substitution patterns including electron-donating as well as electron-withdrawing substituents. More than 16 examples of various isomers of 1,3,4,6-tetraarylated dihydropentalenes have been synthesized in isolated yields of up to 78%, representing a substantial expansion of the range of dihydropentalene scaffolds known to date. Double bond isomerization between the two pentacyclic rings in 1,2-dihydropentalenes with electronically different substituents occurred depending on the polarization of the molecule. The melting points of the air-stable dihydropentalenes decrease, and their solubilities in organic solvents improve with increasing substitution and decreasing symmetry of the molecule. A competitive pseudo-retro-aldol pathway produces 1,3,6-triarylated monocyclic pentafulvenes as side products in yields of 9-68%, which can be cleanly isolated (8 new examples) and used for other synthetic purposes, including separate cyclization to other dihydropentalenes.

Electrochemical Properties and Electrochromism of 6-Aryl-1,3-bis(trimethylsilyl)fulvenes and Their Derivatives

In this study, we have disclosed intriguing electrochromic properties of 6-aryl-1,3-bissilylfulvenes. The electrolyte solutions (0.1 M n-Bu₄NClO₄ in acetonitrile or dichloromethane) of some 6-aryl-1,3-bissilylfulvenes showed notable color changes when superimposed negative voltages were applied to the solutions. Investigation of the substituents at position 6 revealed that the solution of 1,3-bissilyl-6-anthracenylfulvene exhibited chromic changes under both applied superimposed negative and positive voltages and exhibited a three-color electrochromism. Electrochromic properties of 1,6-diarylfulvenes derived from 6-aryl-1,3-bissilylfulvenes were also investigated. The aryl group at position 1 also contributed to the electrochromism of fulvenes.

Density Functional Theory Investigation of Fulvene-Derivatized Fullerenes as Candidates for Organic Solar Cells

Interest within the scientific community in organic solar cells has been on the rise over the last two decades as researchers respond to increasing demands for alternative renewable energy sources. Fulvene, fullerene, and endohedral metallofullerene derivatives have individually shown great promise as efficient charge transfer agents. Despite the heavy demand for research in this area, there have been no studies reported to date that explore the electronic behavior of molecules containing both fullerene and fulvene groups. The lack of interest may be attributed to inherent limitations and inaccuracy in most density functional theory (DFT) band gap calculations for large molecules. Herein we present a systematic computational investigation of the band gaps and dipole moments of several test fullerene-fulvene molecules using a novel DFT method that has been modified to allow accurate computation of the band gaps of this class of molecules. Calculated results showed promising low band gap energies and attractive conductive properties for all fullerene-fulvene derivatives. This new DFT method can conceivably be an invaluable tool that can provide predictive insight into the suitability of similar high molecular weight materials for application in organic solar cell devices.

Reliable Comparison of Pnicogen, Chalcogen, and Halogen Bonds in Complexes of 6-OXF2-Fulvene (X = As, Sb, Se, Te, Be, I) With Three Electron Donors

The pnicogen, chalcogen, and halogen bonds between 6-OXF₂-fulvene (X = As, Sb, Se, Te, Br, and I) and three nitrogen-containing bases (FCN, HCN, and NH₃) are compared. For each nitrogen base, the halogen bond is strongest, followed by the pnicogen bond, and the chalcogen bond is weakest. For each type of bond, the binding increases in the FCN < HCN < NH₃ pattern. Both FCN and HCN engage in a bond with comparable strengths and the interaction energies of most bonds are < -6 kcal/mol. However, the strongest base NH₃ forms a much more stable complex, particularly for the halogen bond with the interaction energy going up to -18 kcal/mol. For the same type of interaction, its strength increases as the mass of the central X atom increases. These bonds are different in strength, but all of them are dominated by the electrostatic interaction, with the polarization contribution important for the stronger interaction. The presence of these bonds changes the geometries of 6-OXF₂-fulvene, particularly for the halogen bond formed by NH₃, where the F-X-F arrangement is almost vertical to the fulvene ring.

Design, Synthesis and In Vitro Anti-Cancer Evaluation of Novel Derivatives of 2-(2-Methyl-1,5-diaryl-1H-pyrrol-3-yl)-2-oxo-N-(pyridin-3- yl)acetamide

OBJECTIVE

Several anti-tubulin agents were introduced for the cancer treatment so far. Despite successes in the treatment of cancer, these agents cause toxic side effects, including peripheral neuropathy. Comparing anti-tubulin agents, indibulin seemed to cause minimal peripheral neuropathy, but its poor aqueous solubility and other potential clinical problems have led to its remaining in a preclinical stage.

METHODS

Herein, indibulin analogues were synthesized and evaluated for their in vitro anti-cancer activity using MTT assay (on the MCF-7, T47-D, MDA-MB231 and NIH-3T3 cell lines), annexin V/PI staining assay, cell cycle analysis, anti-tubulin assay and caspase 3/7 activation assay.

RESULTS

One of the compounds, 4a, showed good anti-proliferative activity against MCF-7 cells (IC50: 7.5 μM) and low toxicity on a normal cell line (IC50 > 100 μM). All of the tested compounds showed lower cytotoxicity on normal cell line in comparison to reference compound, indibulin. In the annexin V/PI staining assay, induction of apoptosis in the MCF-7 cell line was observed. Cell cycle analysis illustrated an increasing proportion of cells in the sub-G-1 phase, consistent with an increasing proportion of apoptotic cells. No increase in G2/M cells was observed, consistent with the absence of anti-tubulin activity. A caspase 3/7 assay protocol showed that apoptosis induction by more potent compounds was due to activation of caspase 3.

CONCLUSION

Newly synthesized compounds exerted acceptable anticancer activity and further investigation of current scaffold would be beneficial.

Correlation of Structure with Crystalline to Amorphous Phase Transitions of 1,3,6-Substituted Fulvene-Derived Molecular Glasses

An investigation into the crystalline to amorphous phase transitions of prepared 1,3,6-substituted pentafulvenes showed the expected reversible heated melt and cooling recrystallization in only a few examples. Systematic incorporation of bulky substituents at the 6-position of the fulvene ring led to the nonreversible thermal behavior, rendering phases that were locked into glassy, vitrified states. These molecular glasses produced physically translucent and amorphous features with glass transition temperatures in the range of 61-77 °C, comparable with high-strength plastics such as polyethylene terephthalate. Additionally, the melting point transitions and the resulting heat of fusion values were found to be directly influenced by the nature of the 6-position substituent. Single crystal X-ray crystallography showed that in some cases, fulvenes possessing fused aromatics exhibited a high degree of intermolecular π-π stacking. These results point to a class of molecular glass formers as host materials possessing tunable bulk properties for potentially new optical applications.

Palladium(II)-Catalyzed Oxidative Decarboxylative [2 + 2 + 1] Annulation of Cinnamic Acids with Alkynes: Access to Polysubstituted Pentafulvenes

An unprecedented palladium(II)-catalyzed oxidative decarboxylative [2 + 2 + 1] annulation of cinnamic acids with alkynes has been developed for the synthesis of polysubstituted pentafulvenes. Ag₂CO₃ and DMSO are essential for the reaction. This protocol features readily available starting materials, a wide substrate scope, and moderate to excellent yields. Moreover, various significant frameworks can be easily obtained from the late-stage transformations of pentafulvenes via oxidation, reduction, and Scholl-type reaction.

Crystal structures of 6-cyclo-propyl-1,3-diphenylfulvene and 6-(2,3-di-meth-oxy-naphth-yl)-1,3-di-phenylfulvene

The title compounds, 6-cyclo-propyl-1,3-diphenylfulvene, C21H18, [systematic name: 5-(cyclo-propyl-methyl-idene)-1,3-di-phen-yl-cyclo-penta-1,3-diene], 1, and 6-(2,3-di-meth-oxy-naphth-yl)-1,3-diphenylfulvene, C30H24O2, {systematic name: 5-[(3,4-di-meth-oxy-naphthalen-2-yl)methyl-idene]-1,3-di-phenyl-cyclo-penta-1,3-di-ene}, 2, were prepared from 1,3-di-phenyl-cyclo-penta-diene, pyrrolidine, and the corresponding aldehydes in an ethano-lic solution. Each structure crystallizes with one mol-ecule per asymmetric unit and exhibits the alternating short and long bond lengths typical of fulvenes. A network of C-H⋯C ring inter-actions as well as C-H⋯O inter-actions is observed, resulting in the compact packing found in each structure.

Heat- or light-induced acylarylation of unactivated alkenes towards 3-(α-acyl) indolines

A heat- or photoredox/iron dual catalysis-enabled rare example of radical acylation across unactivated alkenes with aldehydes.

An overview of the cycloaddition chemistry of fulvenes and emerging applications

The unusual electronic properties and unique reactivity of fulvenes have interested researchers for over a century. The propensity to form dipolar structures at relatively low temperatures and to participate as various components in cycloaddition reactions, often highly selectively, makes them ideal for the synthesis of complex polycyclic carbon scaffolds. As a result, fulvene cycloaddition chemistry has been employed extensively for the synthesis of natural products. More recently, fulvene cycloaddition chemistry has also found application to other areas including materials chemistry and dynamic combinatorial chemistry. This highlight article discusses the unusual properties of fulvenes and their varied cycloaddition chemistry, focussing on applications in organic and natural synthesis, dynamic combinatorial chemistry and materials chemistry, including dynamers, hydrogels and charge transfer complexes. Tables providing comprehensive directories of fulvene cycloaddition chemistry are provided, including fulvene intramolecular and intermolecular cycloadditions complete with reactant partners and their resulting cyclic adducts, which provide a useful reference source for synthetic chemists working with fulvenes and complex polycyclic scaffolds.

New Dyes Based on Extended Fulvene Motifs: Synthesis through Redox Reactions of Naphthoquinones with Donor-Acceptor Cyclopropanes and Their Spectroelectrochemical Behavior

Novel dyes based on extended fulvene motifs are reported. The carbon skeleton was generated by a catalyzed addition of donor-acceptor cyclopropanes to naphthoquinone. The hydroxy group at the central ring of the tricyclic fulvene motif was converted into the triflate, which reacted efficiently with a wide range of nucleophiles, resulting in substitution and thereby providing new derivatives. The synthetic versatility allowed us to investigate the absorption, electrochemical, and UV/Vis-NIR spectroelectrochemical properties of these dyes as a function of the substituents. The dyes were shown to participate in reductive electrochemistry, the reversibility of which can be improved by appropriate selection of the substituents. Additionally, first signs of NIR electrochromism are presented, opening new avenues for the future investigations of such dyes.

Crystal structures of a series of 6-aryl-1,3-diphenyl-fulvenes

The synthesis and crystal structures of a series of 6-aryl-fuvlenes (fulvene is 5-methyl-idene-cyclo-penta-1,3-diene) with varying methyl-ation patterns on the 6-phenyl substituent are reported, namely 6-(3-methyl-phen-yl)-1,3-di-phenyl-fulvene (C25H20), 6-(4-methyl-phen-yl)-1,3-di-phenyl-fulvene (C25H20), 6-mesityl-3-di-phenyl-fulvene (C27H24) and 6-(2,3,4,5,6-penta-methyl-phen-yl)-1,3-di-phenyl-fulvene (C29H28). The bond lengths are typical of those observed in related fulvenes. A network of C-H⋯π ring inter-actions consolidates the packing in each structure.

1,1′-Bis(4-bromophenyl)-3,3′-diphenylferrocene

In the title compound, [Fe(C17H12Br)2], the FeII atom is sandwiched between the eclipsed five-membered rings, with Fe...ring centroid distances of 1.649 (3) and 1.652 (3) Å. In one of the ligands, the Br atom is disordered over two locations [site occupancies = 0.839 (2) and 0.161 (2)].

Design, Synthesis and Anticancer Evaluation of Novel Series of Indibulin Analogues

Background:

Cancer is an important cause of human death worldwide. During the last decades, many anticancer agents with anti-tubulin mechanism have been synthesized or extracted from nature and some of them also entered clinical use. Indibulin is one of the most potent tubulin polymerization inhibitors with minimal peripheral neuropathy, which is a big problem by some of the antimitotic agents such as taxanes and vinka alkaloids. With respect to this giant benefit, herein we decided to design and synthesize novel indibulin related compounds and investigate their anticancer activity against HT-29, Caco-2 and T47-D cancerous cell lines as well as NIH-T3T as normal cell line.

Objective:

The aim of this study was to synthesize new anti-cancer agents and evaluates their cytotoxic activity on diverse cancerous and normal cell lines.

Method:

Target compounds were synthesized in multistep reaction and cytotoxic activity was investigated by MTT cell viability assay.

Results:

Herein, nine novel target compounds were synthesized in moderate to good yield. Some of the compounds exerted good cytotoxic activity against cancerous cell lines. Annexin V/PI staining showed that compound 4g could induce apoptosis and necrosis in HT-29 cell line.

Conclusion:

It is valuable to do further investigation on compound 4g which showed the highest activity against HT-29 and Caco-2 (IC50 values are 6.9 and 7 &µM respectively). Also, synthesis of new derivatives of current synthesized compounds is suggested.

Synthesis and anti-breast cancer activity of novel indibulin related diarylpyrrole derivatives

BACKGROUND

During recent years, a number of anti-tubulin agents were introduced for treatment of diverse types of cancer. Despite their potential in the treatment of cancer, drug resistance and adverse toxicity, such as peripheral neuropathy, are some of the negative effects of anti-tubulin agents. Among anti-tubulin agents, indibulin was found to cause minimal peripheral neuropathy. Thus far, however, indibulin has not entered clinical usage, caused in part by its poor aqueous solubility and other developmental problems in preclinical evaluation.

OBJECTIVES

With respect to need for finding potent and safe anticancer agents, in our current research work, we synthesized several indibulin-related diarylpyrrole derivatives and investigated their anti-cancer activity.

METHODS

Cell cultur studies were perfomred using the MTT cell viability assay on the breast cancer cell lines MCF-7, T47-D, and MDA-MB231 and also NIH-3 T3 cells as representative of a normal cell line. The activity of some of the synthesized compounds for tubulin interaction was studied using colchicine binding and tubulin polymerization assays. The annexin V-FITC/PI method and flow cytometric analysis were used for studying apoptosis induction and cell cycle distribution.

RESULTS AND CONCLUSION

Two of the synthesized compounds, 4f and 4 g, showed high activity on the MDA-MB231 cell line (IC₅₀ = 11.82 and 13.33 μM, (respectively) and low toxicity on the normal fibroblast cells (IC₅₀ > 100 μM). All of the tested compounds were more potent on T47-D cancer cells and less toxic on NIH-3 T3 normal cells in comparison to reference compound, indibulin. The tubulin polymerization inhibition assay and [³H]colchicine binding assay showed that the main mechanism of cell death by the potent synthesized compounds was not related to an interaction with tubulin. In the annexin V/PI staining assay, the induction of apoptosis in the MCF-7 and MDA-MB231 cell lines was observed. Cell cycle analysis illustrated an increased percentage of sub-G-1 cells in the MDA-MB231 cell line as a further indication of cell death through induction of apoptosis. Graphical abstract Novel Indibulin analogous as anti-breast cancer agents.

Palladium-Catalyzed Regio- and Stereoselective Synthesis of ( E)-1,3-Bissilyl-6-arylfulvenes from Aryl Iodides and Silylacetylenes

An efficient synthetic route to ( E)-1,3-bissilyl-6-arylfulvenes has been developed. The reaction of aryl iodides with trimethylsilylacetylene in the presence of a catalytic amount of PdBr₂ gives 6-aryl-1,3-bis(trimethylsilyl)fulvenes in good to excellent yields with complete regio- and stereoselectivity. The reaction involves trimerization of trimethylsilylacetylene and cleavage of one silyl group. The silylated fulvenes obtained could be converted into halogenated fulvenes by site-selective halodesilylation. The halogenated fulvenes underwent the Stille coupling leading to the corresponding arylated fulvenes.

Tetrel Bond between 6-OTX₃-Fulvene and NH₃: Substituents and Aromaticity

Carbon bonding is a weak interaction, particularly when a neutral molecule acts as an electron donor. Thus, there is an interesting question of how to enhance carbon bonding. In this paper, we found that the –OCH₃ group at the exocyclic carbon of fulvene can form a moderate carbon bond with NH₃ with an interaction energy of about −10 kJ/mol. The –OSiH₃ group engages in a stronger tetrel bond than does the –OGeH₃ group, while a reverse result is found for both –OSiF₃ and –OGeF₃ groups. The abnormal order in the former is mainly due to the stronger orbital interaction in the –OSiH₃ complex, which has a larger deformation energy. The cyano groups adjoined to the fulvene ring not only cause a change in the interaction type, from vdW interactions in the unsubstituted system of –OCF₃ to carbon bonding, but also greatly strengthen tetrel bonding. The formation of tetrel bonding has an enhancing effect on the aromaticity of the fulvene ring.

Coordination complexes of chromium(0) with a series of 1,3-diphenyl-6-aryl-fulvenes

The synthesis and structural properties of a series of chromium tricarbonyl 'piano-stool' complexes bearing substituted penta-fulvene ligands were studied. The complexes, tricarbon-yl(1,3,6-tri-phenyl-fulvene)chromium(0) benz-ene hemisolvate, [Cr(C24H18)(CO)3]·0.5C6H6 (I), tricarbon-yl[1,3-di-phen-yl-6-(3-vinyl-phen-yl)fulvene]chromium(0), [Cr(C26H20)(CO)3] (II), and tricarbon-yl[1,3-diphenyl-6-(pyren-1-yl)fulvene]chromium(0), [Cr(C34H22)(CO)3] (III), each have a distorted octa-hedral geometry, with the fulvene coordinated in a π-η2:π-η2:π-η2 fashion. Significant deviation of the exocyclic fulvene double bond from the cyclo-penta-diene plane accompanies coordination. Evidence of non-covalent π-π inter-actions was observed in both (I) and (III), with centroid-to-centroid distances ranging from 3.330 (8) to 3.494 (8) Å.

Design, synthesis and cytotoxicity evaluation of indibulin analogs

Indibulin is one of the most potent tubulin polymerization inhibitors with minimal peripheral neuropathy. The design and synthesis of new indibulin analogs were carried out in order to investigate their anti-cancer activity. The target compounds 4a–i were synthesized in multistep reactions starting with the related indole derivatives. Compound 4f shows the highest cytotoxic activity on HT-29 and Caco-2 cell lines with the respective half maximal inhibitory concentration (IC50) values of 5.1 μm and 7.3 μm. In the case of the T47-D cell line, compound 4c exerts the best cytotoxic activity with an IC50 value of 11.5 μm. In the cell cycle analysis on HT-29 cells, compound 4f at 5.1 μm showed an increase in the percentage of cells in the sub-G1 phase. Altogether, nine target compounds were synthesized and characterized by infrared spectroscopy (IR), proton nuclear magnetic resonance (1H NMR), carbon-13 nuclear magnetic resonance (13C NMR), mass spectrometry (MS) and elemental analysis. Some of the compounds show good cytotoxic activity against cancerous cell lines.

9-(3,5-Dimethylbenzylidene)-8-(3,5-dimethylphenyl)-1,3,5,7-tetraphenyl-2,4,7,8-tetrahydro-4,7-methanoazulene acetonitrile disolvate

The title Diels–Alder product, C52H44·2CH3CN, was obtained in trace quantity as the `endo' isomer during the synthesis of 1,3-diphenyl-6-(3,5-dimethylphenyl)fulvene. One of the two co-crystallized acetonitrile molecules is linked to the main molecule by a weak C—H...N hydrogen bond.

Predicting reduction potentials of 1,3,6-triphenyl fulvenes using molecular electrostatic potential analysis of substituent effects

The influence of mono- and multiple substituent effect on the reduction potential (E⁰ ) of 1,3,6-triphenyl fulvenes is investigated using B3LYP-SMD/6-311+G(d,p) level density functional theory. The molecular electrostatic potential (MESP) minimum at the fulvene π-system (V_min ) and the change in MESP at any of the fulvene carbon atoms (ΔV_C ) for both neutral and reduced forms are used as excellent measures of substituent effect from the para and meta positions of the 1,3 and 6-phenyl moieties. Substitution at 6-phenyl para position has led to significant change in E⁰ than any other positions. By applying the additivity rule of substituent effects, an equation in ΔV_C is derived to predict E⁰ for multiply substituted fulvenes. Further, E⁰ is predicted for a set of 2000 hexa-substituted fulvene derivatives where the substituents and their positions in the system are chosen in a random way. The calculated E⁰ agreed very well with the experimental E⁰ reported by Godman et al. Predicting E⁰ solely by substituent effect offers a simple and powerful way to select suitable combinations of substituents on fulvene system for light harvesting applications. © 2018 Wiley Periodicals, Inc.

Palladium-Catalyzed C-H Bond Functionalization of 6,6-Diphenylfulvenes: An Easier Access to C1-Arylated and C1,C4-Diarylated Fulvenes

Conditions allowing the palladium-catalyzed regioselective direct arylation of fulvene derivatives are reported. The nature of the aryl source exhibits an important influence on the yield. The reaction of fulvenes with aryl bromides gave poor yields, whereas the use of benzenesulfonyl chlorides gave rise to fulvenes arylated at C1- and C4-positions on the 5-membered ring in good yields. The reaction tolerates various substituents such as nitrile, nitro, fluoro, trifluoromethyl, chloro, or even bromo on the benzenesulfonyl chloride.

First preparation of low band gap fulvene-modified polynorbornene via ring-opening metathesis polymerization

New polymers containing intact pendant-fulvene moieties have been successfully prepared from 1,3-phenyl-6-norbornenylfulvene via ring-opening metathesis polymerization (ROMP). The prepared polyfulvenes have unique electrochemical and photophysical properties which make them interesting candidates for light harvesting materials.

Efficient strategy for construction of 6-carbamoylfulvene-6-carboxylate skeletons via [3 + 2] cycloaddition of 1-cyanocyclopropane 1-ester with β-nitrostyrenes

An efficient and straightforward the preparation of 6-carbamoylfulvene-6-carboxylates via a cycloaddition reaction between 1-cyanocyclopropane 1-ester and β-nitrostyrenes.

3-(4-Bromo-phen-yl)cyclo-pent-2-en-1-one

In the title compound, C11H9BrO, the cyclo-pentenone ring is almost planar with an r.m.s. deviation of 0.0097 Å. The largest inter-ring torsion angles [2.4 (3), 1.3 (3) and 3.53 (2)°] reveal only a very small twist between the rings, and suggest that the two rings are conjugated. The mol-ecule is slightly bowed, as shown by the small dihedral angle between the rings [5.3 (1)°]. The crystal packing pattern consists of parallel sheets that stack parallel to the ac plane. Each sheet consists of mol-ecules that pack side-to-side with the same relative orientation of phenyl and cyclo-pentenone rings along the a- and c-axis directions. Slipped side-to-side, face-to-face and edge-to-face inter-actions exist between pairs of sheets with edge-to-edge and edge-to-face O⋯H-C(sp (2)) weak hydrogen-bond contacts. A relatively short edge-to-face contact (2.77 Å) also exists between pairs of sheets.

Symmetrical bis(fulvene) chromophores: model compounds for acceptor–donor–acceptor dye architectures

A facile method for synthesizing conjugated bis(fulvenes) demonstrates tailorable optical band gaps and serves as a model dye system for new organic electronic applications.

Expanding the chemical structure space of opto-electronic molecular materials: unprecedented push-pull chromophores by reaction of a donor-substituted tetracyanofulvene with electron-rich alkynes

The reaction of a 3,5-bis(N,N-dimethylanilino)-substituted 2,4,6,6-tetracyanopentafulvene (TCPF) with mono- and bis(N,N-dimethylanilino)acetylene provides facile access to push-pull chromophores with diverse new scaffolds. The starting TCPF reacts with bis(N,N-dimethylanilino)acetylene in a formal [2+2] cycloaddition at the exocyclic double bond, followed by retroelectrocyclization, to yield an ethenylene-extended push-pull pentafulvene. The transformation with 4-ethynyl-N,N-dimethylaniline also yields a similar extended pentafulvene as well as two other products that required X-ray analysis for their structure elucidation. One features an 8,8-dicyanoheptafulvene core formed by formal [2+2] cycloaddition, followed by ring opening via fragmentation. The second is a chiral cyclobutenylated tetrahydropentalene, resulting from a cascade of formal [6+2] and [2+2] cycloadditions. All new nonplanar push-pull chromophores display amphoteric redox behavior with both strong electron-donating and -accepting potency. Notably, the N,N-dimethylanilino-substituted extended pentafulvenes show remarkably low oxidation potentials (0.27/0.28 V vs Fc/Fc(+) reference) that are lower than those for N,N-dimethylaniline itself. The push-pull-substituted extended pentafulvenes feature intense electronic absorption bands, extending over the entire visible spectral range into the near infrared, and low highest occupied molecular orbital-lowest unoccupied molecular orbital gaps. These properties, together with high thermal stability and good solubility, suggest the potential use of the new chromophores as advanced materials in molecular electronics devices.