Rotational Isomerism Involving Acetylene Carbon

Synthesis of a novel twisted π-conjugated macrocycle via double Friedel-Crafts reaction and its physical properties

We synthesized a cyclic molecule from diarylalkynes and Meldrum's acid derivatives as the methylenation reagent via double Friedel-Crafts reaction. Single-crystal X-ray structure analysis confirmed the twisted structure of the molecule. We also investigated their physical properties and homoconjugation by UV-Vis, photoluminescence, DFT and TD-DFT calculations.

Rh(III)-catalyzed atroposelective C-H alkynylation of 1-aryl isoquinolines with hypervalent iodine-alkyne reagents

An efficient Rh(III)-catalyzed enantioselective C-H alkynylation of isoquinolines is disclosed. The C-H alkynylation of 1-aryl isoquinolines with hypervalent iodine-alkyne reagents proceeded in DMA at room temperature in the presence of 2.5 mol% chiral SCpRh(III) complex along with 20 mol% AgSbF6, providing axially chiral alkynylated 1-aryl isoquinolines in excellent yields (up to 93%) and enantioselectivity (up to 95% ee). The diverse transformations of the product further enhance the potential utility of this reaction.

Rapid Access to Encapsulated Molecular Rotors via Coordination-Driven Macrocycle Formation

Macrocycle formation that relies upon trans metal coordination of appropriately placed pyridine ligands within an arylene ethynylene construct provides rapid and reliable access to molecular rotators encapsulated within macrocyclic stators. Showing no significant close contacts to the central rotators, X-ray crystallography of AgI -coordinated macrocycles provides plausibility for unobstructed rotation or wobbling of rotators within the central cavity. Solid-state 13 C NMR of PdII -coordinated macrocycles supports the notion of unobstructed movement of simple arenes in the crystal lattice. Solution 1 H NMR studies indicate complete and immediate macrocycle formation upon the introduction of PdII to the pyridyl-based ligand at room temperature. Moreover, the formed macrocycle is stable in solution; a lack of significant changes in the 1 H NMR spectrum upon cooling to -50 °C is consistent with the absence of dynamic behavior. The synthetic route to these macrocycles is expedient and modular, providing access to rather complex constructs in four simple steps involving Sonogashira coupling and deprotection reactions.

NHC-mediated photocatalytic deoxygenation of alcohols for the synthesis of internal alkynes via a Csp3-Csp coupling reaction

NHC-mediated deoxygenation of alcohols under photocatalytic conditions is described. The process provides various alkyl radicals, which can react with 1-bromoalkyne via Csp3-Csp coupling to afford internal alkynes in moderate to good yields. The method offers a new and convenient approach to synthesize internal alkynes.

Visible-Light-Mediated Deacylated Alkynylation of Unstrained Ketone

Deconstructive alkynylation of an unstrained ketone catalyzed by an organic photocatalyst under blue light irradiation is reported for the first time. A broad substrate scope with up to 63 examples, excellent functional group tolerance, and gram scale reaction demonstrated the practicality of this novel alkynylation method. The dihydroquinazolinone derivative of trifluoroacetophenone had been proved to have potential as a novel trifluoromethylation reagent after working well for the trifluoromethylation reaction with various alkynyl bromides.

Synthesis, Structures, and Complexation with Phenolic Guests of Acridone-Incorporated Arylene-Ethynylene Macrocyclic Compounds

Acridone units were incorporated into the arylene-ethynylene structure as polar arene units. Cyclic trimers consisting of three acridone-2,7-diyl units and three 1,3-phenylene units were synthesized by Sonogashira couplings via stepwise or direct route. X-ray analysis revealed that the trimer had a nearly planar macrocyclic framework with a cavity surrounded by three carbonyl groups. In contrast, the corresponding tetramer had a nonplanar macrocyclic framework. ¹ H NMR measurements showed that the trimer formed a 1 : 1 complex as a macrocyclic host with dihydric phenol guests, and the association constants were determined to be ca. 1.0×10³  L mol^-1 for hydroquinone or resorcinol guests in CDCl₃ at 298 K. The calculated structures of these complexes by the DFT method supported the presence of two sets of OH⋅⋅⋅O=C hydrogen bonds between the host and guest molecules. The spectroscopic data of the cyclic trimers and tetramers are compared with those of reference acridone compounds.

Dimorpholinoacetylene and Its Use for the Synthesis of Tetraaminocyclobutadiene Species

The new diaminoacetylene (DAA) dimorpholinoacetylene (3) was prepared from 1,1-dimorpholinoethene (1) by bromination to form the dibromoketene aminal 2, which upon lithiation afforded 3 through a Fritsch-Buttenberg-Wiechell rearrangement. Heating 3 at elevated temperatures resulted in a complete conversion into the dimer 1,1,2,4-tetramorpholino-1-buten-3-yne (4), which was used for the synthesis of four-membered cyclic bent allene (CBA) transition-metal complexes of the type [(CBA)MLn ] (5-7; MLn =AuCl, RhCl(COD), RhCl(CO)2 ; CBA=1,3,4,4-tetramorpholino-1,2-cyclobutadiene; COD=1,5-cyclooctadiene). The reaction of 3 with tetraethylammonium bromide gave 1,2,3,4-tetramorpholinocyclobutenylium bromide (8), which reacted with bromine to form 1,2,3,4-tetra(morpholino)cyclobutenediylium bis(tribromide) (9). Compound 9 represents the first fully characterized compound containing a tetraaminocyclobutadiene dication and displays a nearly planar C4 N4 core as shown by X-ray diffraction analysis. Detailed quantum chemical calculations were performed to assess the aromaticity of tetraaminocyclubutadiene dications by employing the Nucleus Independent Chemical Shift (NICS) method and current density analysis.

Rigid Bay-Conjugated Perylene Bisimide Rotors: Solvent-Induced Excited-State Symmetry Breaking and Resonance-Enhanced Two-Photon Absorption

Intramolecular charge transfer and excited-state symmetry breaking have a significant effect on the nonlinear optical properties of multipolar chromophores. Rigid and nonplanar perylene bisimide derivatives (PBIs) functionalized at bay positions were comparatively and comprehensively investigated. In apolar solvents, two quadrupolar molecular rotors showed an obvious decrease of the A_0-0/A_0-1 ratios, suggesting strong exciton coupling with the adjacent PBI units initiated by the π-π stacking. The vanishment of the preferable dimer emission in polar solvents supported the plausible phenomena of excited-state symmetry breaking, thanks to the facile rotation around the rigid linkers. Comparative femtosecond transition absorption studies confirmed their notable differences in relaxation dynamics and the generation of radical anions (PBI^•-) and cations (PBI^•+). The maxima two-photon absorption (2PA) wavelengths obtained for the molecular rotors were slightly red-shifted to 670 nm with intrinsic resonance-enhanced characteristics, reflecting the synergistic effect of functional positions and molecular architectures. Meanwhile, the obvious increase of significant 2PA cross-section values in polar solvents illustrated the stabilization of the symmetry-broken dipolar states. Further femtosecond Z-scan also manifested the contribution of excited-state dynamics on the nonlinear optical properties of multipolar chromophores.

Martini 3 coarse-grained force field for poly(para-phenylene ethynylene)s

Poly(para-phenylene ethynylene)s, or short PPEs, are a class of conjugated and semi-flexible polymers with a strongly delocalized π electron system and increased chain stiffness. Due to this, PPEs have a wide range of technological applications. Although the material properties of single-chains or mixtures of few PPE chains have been studied in detail, the properties of large assemblies remain to be fully explored. Here, we developed a coarse-grained model for PPEs with the Martini 3 force field to enable computational studies of PPEs in large-scale assembly. We used an optimization geometrical approach to take the shape of the π conjugated backbone into account and also applied an additional angular potential to tune the mechanical bending stiffness of the polymer. Our Martini 3 model reproduces key structural and thermodynamic observables of single PPE chains and mixtures, such as persistence length, density, packing and stacking. We show that chain entanglement increases with the expense of nematic ordering with growing PPE chain length. With the Martini 3 PPE model at hand, we are now able to cover large spatio-temporal scales and thereby to uncover key aspects for the structural organization of PPE bulk systems. The model is also predicted to be of high applicability to investigate out-of-equilibrium behavior of PPEs under mechanical force.

Conformational polymorphs of isotretinoin and their impact on physicochemical and biological properties

Isotretinoin is the first-line drug for treatment of severe acne. Only one polymorph was reported even though it has been launched for nearly 40 years, and its clinic application was however limited by its stability and solubility challenges. In our study, two new polymorphs of isotretinoin were discovered and fully characterized. The transformation relationships between these solid forms were fully discussed, and a visible color change during single-crystal-to-single-crystal phase transition with the conformational change was investigated. Form II is determined to be thermodynamic stable form at room temperature, but metastable form at body temperature. The results show that form II is an ideal solid state possessing both superior thermal stability (60℃, open air) and higher absorption once delivered into body. The thermal stability can be associated with the crystal structure such as torsion angle. The relative bioavailability of form II is higher than form I as expected, and the bioavailability of form II formulation is about 2 times as that of the marketed form I capsule. Therefore, form II formulation could provide an alternative for better performing isotretinoin.

Synthesis and Photophysics of Water-Soluble Psoralens with Red-Shifted Absorption

8-Methoxypsoralen (8-MOP) serves as a PUVA (psoralen + UV-A) agent in the treatment of certain skin diseases. Derivatives of 8-MOP with cationic aromatic substituents at the five positions were synthesized and characterized by steady-state, femtosecond and nanosecond spectroscopy as well as cyclic voltammetry. The aromatic substituents' positive charge increases the water solubility and the affinity toward intercalation into DNA. The aromatic substituents were supposed to lower the psoralen S₁ energy and thereby suppress a photo-induced electron transfer (PET) with guanine-bearing DNA. Such a suppression of this PET is expected to increase the propensity of psoralens to photo-addition to DNA. For derivatives bearing methylpyridinium residues, femtosecond spectroscopy revealed an intramolecular PET occurring on the picosecond time scale. This PET precludes the population of the triplet state. As triplet states are the precursor state for the photo-addition to DNA, their intermolecular PET renders these derivatives ineffective in terms of PUVA. For two derivatives bearing trimethylphenylammonium moieties, such an intramolecular PET does not occur and the triplet state is populated. Surprisingly, these compounds also exhibit no PUVA activity. Based on these findings, implications for further optimization of PUVA agents are discussed.

Folding-controlled assembly of ortho-phenylene-based macrocycles

The self-assembly of foldamers into macrocycles is a simple approach to non-biological higher-order structure. Previous work on the co-assembly of ortho-phenylene foldamers with rod-shaped linkers has shown that folding and self-assembly affect each other; that is, the combination leads to new emergent behavior, such as access to otherwise unfavorable folding states. To this point this relationship has been passive. Here, we demonstrate control of self-assembly by manipulating the foldamers' conformational energy surfaces. A series of o-phenylene decamers and octamers have been assembled into macrocycles using imine condensation. Product distributions were analyzed by gel-permeation chromatography and molecular geometries extracted from a combination of NMR spectroscopy and computational chemistry. The assembly of o-phenylene decamers functionalized with alkoxy groups or hydrogens gives both [2 + 2] and [3 + 3] macrocycles. The mixture results from a subtle balance of entropic and enthalpic effects in these systems: the smaller [2 + 2] macrocycles are entropically favored but require the oligomer to misfold, whereas a perfectly folded decamer fits well within the larger [3 + 3] macrocycle that is entropically disfavored. Changing the substituents to fluoro groups, however, shifts assembly quantitatively to the [3 + 3] macrocycle products, even though the structural changes are well-removed from the functional groups directly participating in bond formation. The electron-withdrawing groups favor folding in these systems by strengthening arene–arene stacking interactions, increasing the enthalpic penalty to misfolding. The architectural changes are substantial even though the chemical perturbation is small: analogous o-phenylene octamers do not fit within macrocycles when perfectly folded, and quantitatively misfold to give small macrocycles regardless of substitution. Taken together, these results represent both a high level of structural control in structurally complex foldamer systems and the demonstration of large-amplitude structural changes as a consequence of a small structural effects.

The folding propensity of ortho-phenylene foldamers dictates the outcome of their self-assembly into macrocycles.

Cross-Coupled Phenyl- and Alkynyl-Based Phenanthrolines and Their Effect on the Photophysical and Electrochemical Properties of Heteroleptic Cu(I) Photosensitizers

With the aims of increasing the antenna system and improving the photophysical properties of Cu(I)-based photosensitizers, the backbone of 2,9-dimethyl-1,10-phenanthroline was selectively extended in the 5,6-position. Applying specifically tailored Suzuki-Miyaura and "chemistry-on-the-complex" Sonogashira cross-coupling reactions enabled the development of two sets of structurally related diimine ligands with a broad variety of different phenyl- and alkynyl-based substituents. The resulting 11 novel heteroleptic Cu(I) complexes, including five solid-state structures, were studied with respect to their structure-property relationships. Both sets of substituents are able to red-shift the absorption maxima and to increase the absorptivity. For the alkynyl-based complexes, this is accompanied by a significant anodic shift of the reduction potentials. The phenyl-based substituents strongly influence the emission wavelength and quantum yield of the resulting Cu(I) complexes and lead to an increase in the emission lifetime of up to 504 ns, which clearly indicates competition with the benchmark system [(xantphos)Cu(bathocuproine)]PF₆.

Gold-Catalyzed Annulation of 1,8-Dialkynylnaphthalenes: Synthesis and Photoelectric Properties of Indenophenalene-Based Derivatives

A simple gold-catalyzed annulation of 1,8-dialkynylnaphthalenes utilizing a cationic gold catalyst was developed. Such a peri-position of two alkynyl substituents has not been studied in gold catalysis before. Dependent on the substrate, the reactions either follow a mechanism involving vinyl cation intermediates or involve a dual gold catalysis mechanism which in an initial 6-endo-dig-cyclization generates gold(I) vinylidene intermediates that are able to insert into C-H bonds. Indenophenalene derivatives were obtained in moderate to high yields. In addition, the bidirectional gold-catalyzed annulation of tetraynes provided even larger conjugated π-systems. The optoelectronic properties of the products were also investigated.

Ligand-free Pd/Ag-mediated dehydrogenative alkynylation of imidazole derivatives

A variety of 2-alkynyl(benzo)imidazoles have been synthesized by dehydrogenative alkynylation of (benzo)imidazoles with terminal alkyne in NMP under air in the presence of Ag₂CO₃ as the oxidant and Pd(OAc)₂ as the catalyst precursor. The data obtained in this study support a reaction mechanism involving a non-concerted metalation deprotonation (n-CMD) pathway.

The regioselective synthesis of 2-alkynyl(benz)imidazoles was successfully achieved by Pd(ii)/Ag(i)-mediated dehydrogenative alkynylation of the corresponding (benz)imidazoles with terminal alkynes in an open vessel.

A Doubly Bridged Bis(phenylethynyl)benzene: Different from a Twisted Tolan

The synthesis of a doubly bridged 1,4‐bis(phenylethynyl)benzene is reported. The target displays photophysical properties, distinctly different from that of its congeners, the singly bridged tolans. Quantum‐chemical calculations suggest a lack of planarization of the bridged bis(phenylethynyl)benzene in the first excited state.

Copper-Catalyzed Oxidative Cross-Coupling of Electron-Deficient Polyfluorophenylboronate Esters with Terminal Alkynes

We report herein a mild procedure for the copper-catalyzed oxidative cross-coupling of electron-deficient polyfluorophenylboronate esters with terminal alkynes. This method displays good functional group tolerance and broad substrate scope, generating cross-coupled alkynyl(fluoro)arene products in moderate to excellent yields. Thus, it represents a simple alternative to the conventional Sonogashira reaction.

Synthesis, Structures, and Properties of Highly Strained Cyclophenylene-Ethynylenes with Axial and Helical Chirality

Single and double cyclophenylene-ethynylenes (CPEs) with axial and helical chirality have been synthesized by the Sonogashira cross-coupling of di- and tetraethynyl biphenyls with a U-shaped prearomatic diiodoparaphenylene followed by reductive aromatization. X-ray crystallographic analyses and DFT calculations revealed that the CPEs possess highly twisted bent structures. Bend angles on the edge of the paraphenylene units were close to the value of [5]cycloparaphenylene (CPP)-the smallest CPP to date. The double and single CPEs possessed stable chirality despite flexible biphenyl structures because of the high strain in the diethynyl-paraphenylene moiety. In both the single and double CPEs, orbital interactions along the biphenyl axis were observed by DFT calculations in LUMO and LUMO+2 of the single CPE and LUMO+1 of the double CPE, which likely cause lowering of these orbital energies. Concerning chiroptical properties: boosting of the g_abs value was observed in the biphenyl-based double CPE, as well as the binaphthyl-based single CPE, compared to the biphenyl-based single CPE.

Copper-catalysed Csp3–Csp cross-couplings between cyclobutanone oxime esters and terminal alkynes induced by visible light

A novel transformation for the construction of Csp³–Csp bonds was achieved via a photo-induced copper-catalysed C–C bond cleavage.

The positional isomerism in bimetal nanoclusters

Enriching the variety of isomerism in the nanocluster field is exciting but challenging.

Triple-Pnictogen Bonding as a Tool for Supramolecular Assembly

Supramolecular assembly utilizing simultaneous formation of three pnictogen bonds around a single antimony vertex was explored via X-ray crystallography, solution NMR, and computational chemistry. An arylethynyl (AE) ligand was designed to complement the three electrophilic regions around the Sb compound. Though solution studies reveal large binding constants for individual pyridyl units with the Sb donor, the rigidity and prearrangement of the AE acceptor proved necessary to achieve simultaneous binding of three acceptors to the Sb-centered pnictogen-bond donor. Calculations and X-ray structures suggest that negative cooperativity upon sequential binding of three acceptors to a Sb center limits the utility of triple-pnictogen bonding pyridyl acceptors. These limitations can be negated, however, when positive cooperativity is designed into a complementary acceptor ligand.

Macrocycles of higher ortho-phenylenes: assembly and folding

The sizes and geometries of macrocycles assembled from ortho-phenylenes are predicted by the stabilities and bite angles of possible conformers.

Higher-order structure in abiotic foldamer systems represents an important but largely unrealized goal. As one approach to this challenge, covalent assembly can be used to assemble macrocycles with foldamer subunits in well-defined spatial relationships. Such systems have previously been shown to exhibit self-sorting, new folding motifs, and dynamic stereoisomerism, yet there remain important questions about the interplay between folding and macrocyclization and the effect of structural confinement on folding behavior. Here, we explore the dynamic covalent assembly of extended ortho-phenylenes (hexamer and decamer) with rod-shaped linkers. Characteristic ¹H chemical shift differences between cyclic and acyclic systems can be compared with computational conformer libraries to determine the folding states of the macrocycles. We show that the bite angle provides a measure of the fit of an o-phenylene conformer within a shape-persistent macrocycle, affecting both assembly and ultimate folding behavior. For the o-phenylene hexamer, the bite angle and conformer stability work synergistically to direct assembly toward triangular [3 + 3] macrocycles of well-folded oligomers. For the decamer, the energetic accessibility of conformers with small bite angles allows [2 + 2] macrocycles to be formed as the predominant species. In these systems, the o-phenylenes are forced into unusual folding states, preferentially adopting a backbone geometry with distinct helical blocks of opposite handedness. The results show that simple geometric restrictions can be used to direct foldamers toward increasingly complex folds.

Nonconjugated Hydrocarbons as Rigid-Linear Motifs: Isosteres for Material Sciences and Bioorganic and Medicinal Chemistry

Nonconjugated hydrocarbons, like bicyclo[1.1.1]pentane, bicyclo[2.2.2]octane, triptycene, and cubane are a unique class of rigid linkers. Due to their similarity in size and shape they are useful mimics of classic benzene moieties in drugs, so-called bioisosteres. Moreover, they also fulfill an important role in material sciences as linear linkers, in order to arrange various functionalities in a defined spatial manner. In this Review article, recent developments and usages of these special, rectilinear systems are discussed. Furthermore, we focus on covalently linked, nonconjugated linear arrangements and discuss the physical and chemical properties and differences of individual linkers, as well as their application in material and medicinal sciences.

Intramolecular benzoallene–alkyne cycloaddition initiated by site-selective SN2′ reaction of epoxytetracene en route to π-extended pyracylene

A new synthetic route to π-extended pyracylene was developed by hydrogen halide promoted cascade reaction of epoxytetracene.

Tetrakis(phenylethynyl)tetracene: A New π-Extended Rubrene Derivative

An efficient synthetic route to 5,6,11,12-tetrakis(arylethynyl)tetracenes, new π-extended rubrene derivatives, was developed by means of [2+4] cycloaddition of dialkynylnaphthalyne and dialkynylisobenzofuran. Importantly, two alkynyl groups introduced into the aryne exerts a significant effect in lowering the LUMO energy, allowing practical access to sterically overcrowded polycyclic structures through an efficient HOMO-LUMO interaction. Study on the potential reactivity inherent in the peri-ethynyl-substituted tetracenes revealed several interesting reactivities. X-ray analysis of these new π-extended derivatives showed distorted structures to reduce steric repulsion due to the existence of the substituents at the peri-positions.

A Tethered Tolane: Twisting the Excited State

The synthesis of a doubly bridged tolane is reported. The target is obtained in a five-step synthesis, starting from commercially available 2-amino-meta-xylene by a combination of a Sandmeyer reaction, radical bromination, and Stille-type coupling, followed by double ring closing. The doubly tethered tolane is crystalline; the two phenyl rings are highly twisted with respect to each other both in solution and in the solid state. Optical spectroscopy and quantum chemical calculations show that the doubly bridged tolane is twisted not only in the ground state, but also in the excited state, leading to emission from the twisted state in solution and in the solid state. Strong phosphorescence is observed at cryogenic temperatures.

Synthesis and Electronic Properties of Length-Defined 9,10-Anthrylene-Butadiynylene Oligomers

Linear π-conjugated oligomers consisting of anthracene and diacetylene units were readily synthesized by a one-pot process that involved desilylation and oxidative coupling from appropriate building units. We were able to isolate length-defined oligomers ranging from 2-mer to 6-mer as stable and soluble solids. The bathochromic shifts in the UV-vis spectra suggested that the π-conjugation was extended with elongation of the linear chain. Cyclic voltammetric measurements showed characteristic reversible oxidation waves that were dependent on the number of anthracene units.

1,8-Diphenyl-9,10-Bis(arylethynyl)phenanthrenes: Synthesis, Distorted Structure, and Optical Properties

The synthesis and optical properties of 1,8-diphenyl-9,10-bis(arylethynyl)phenanthrenes, which are distorted phenanthrenes, are reported. The presence of the two phenyl groups at the 1,8-positions of phenanthrene significantly distorts the molecular geometries, as was evidenced by X-ray crystallography. The congested substitution pattern in the K region results in a distorted aromatic framework, which leads to a redshift in the emission spectrum. These observations are in stark contrast to 9,10-bis(phenylethynyl)phenanthrene with no phenyl groups at the 1,8-positions. A large Stokes shift suggested extensive structural relaxation between the phenyl and arylethynyl units in the excited state, which was supported by theoretical calculations.

From the Synthesis of Nanovehicles to Participation in the First Nanocar Race-View from the French Team

This review article presents our accomplished work on the synthesis of molecular triptycene wheels and their introduction into nanovehicles such as wheelbarrows and nanocars, equipped with two and four wheels, respectively. The architecture of nanovehicles is based on polycyclic aromatic hydrocarbons, which provide a potential cargo zone. Our strategy allowed us to obtain planar or curved nanocars, exhibiting different mobilities on metallic surfaces. Our curved nanocar participated in the first nanocar race organized in Toulouse (France) on 28 and 29 April 2017.

Getting excited: challenges in quantum-classical studies of excitons in polymeric systems

A combination of classical molecular dynamics (MM/MD) and quantum chemical calculations based on the density functional theory (DFT) was performed to describe the conformational properties of diphenylethyne (DPE), methylated-DPE and poly para phenylene ethynylene (PPE). DFT calculations were employed to improve and develop force field parameters for MM/MD simulations. Many-body Green's function theory within the GW approximation and the Bethe-Salpeter (GW-BSE) equation were utilized to describe the excited states of the systems. The reliability of the excitation energies based on the MM/MD conformations was examined and compared to the excitation energies from DFT conformations. The results show an overall agreement between the optical excitations based on MM/MD conformations and DFT conformations. This allows for the calculation of excitation energies based on MM/MD conformations.

X-ray Generated Recombination Exciplexes of Substituted Diphenylacetylenes with Tertiary Amines: A Versatile Experimental Vehicle for Targeted Creation of Deep-Blue Electroluminescent Systems

Customizable and technology-friendly functional materials are one of the mainstays of emerging organic electronics and optoelectronics. We show that recombination exciplexes of simple substituted diphenylacetylenes with tertiary amines can be a convenient source of tunable deep-blue emission with possible applications in organic electroluminescent systems. The optically inaccessible exciplexes were produced via recombination of radiation-generated radical ion pairs in alkane solution, which mimics charge transport and recombination in the active layer of practical organic light-emitting diodes in a simple solution-based experiment. Despite varying and rather poor intrinsic emission properties, diphenylacetylene and its prototypical methoxy (donor) or trifluoromethyl (acceptor) monosubstituted derivatives readily form recombination exciplexes with N,N-dimethylaniline and other tertiary amines that produce emission with maxima ranging from 385 to 435 nm. The position of emission band maximum linearly correlates with readily calculated gas-phase electron affinity of the corresponding diphenylacetylene, which can be used for fast computational prescreening of the candidate molecules, and various substituted diphenylacetylenes can be synthesized via relatively simple and universal cross-coupling reactions of Sonogashira and Castro. Together, the simple solution-based experiment, computationally cheap prescreening method, and universal synthetic strategy may open a very broad and chemically convenient class of compounds to obtain OLEDs and OLED-based multifunctional devices with tunable emission spectrum and high conversion efficiency that has yet not been seriously considered for these purposes.

Pd(ii)-Catalyzed gamma-C(sp3)–H alkynylation of amides: selective functionalization of R chains of amides R1C(O)NHR

The first example of palladium(ii)-catalyzed alkynylation of an unactivated gamma C(sp³)–H bond of alkyl amides (cyclic, linear, and amino acids) is reported.

Conformational switching via an intramolecular H-bond modulates the fluorescence lifetime in a novel coumarin–imidazole conjugate

Achieving synthetic control over light-driven molecular dynamics is essential for designing complex molecule-based devices.

Rh(iii)-Catalyzedortho-C–H alkynylation ofN-phenoxyacetamides with hypervalent iodine-alkyne reagents at room temperature

Directing group ONHR preservedortho-alkynylation under mild conditions catalyzed by rhodium is reported.

The effect of the cobalt and manganese central metal ions on the nonlinear optical properties of tetra(4-propargyloxyphenoxy)phthalocyanines

The phthalocyanines were investigated as optical limiters. The paramagnetic complexes were not effective owing to quenching of the excited states.