The B2PLYP double hybrid functional, coupled with the correlation-consistent triple-ζ cc-pVTZ (VTZ) basis set, has been validated in the framework of the semiexperimental (SE) approach for deriving ...accurate equilibrium structures of molecules containing up to 15 atoms. A systematic comparison between new B2PLYP/VTZ results and several equilibrium SE structures previously determined at other levels, in particular B3LYP/SNSD and CCSD(T) with various basis sets, has put in evidence the accuracy and the remarkable stability of such model chemistry for both equilibrium structures and vibrational corrections. New SE equilibrium structures for phenylacetylene, pyruvic acid, peroxyformic acid, and phenyl radical are discussed and compared with literature data. Particular attention has been devoted to the discussion of systems for which lack of sufficient experimental data prevents a complete SE determination. In order to obtain an accurate equilibrium SE structure for these situations, the so-called templating molecule approach is discussed and generalized with respect to our previous work. Important applications are those involving biological building blocks, like uracil and thiouracil. In addition, for more general situations the linear regression approach has been proposed and validated.
Gold‐catalyzed cycloadditions of ynamides with azidoalkenes or 2H‐azirines give 3+2 or 4+3 formal cycloadducts of three classes. Cycloadditions of ynamides with 2H‐azirine species afford pyrrole ...products with two regioselectivities when the Cβ‐substituted 2H‐azirine is replaced from an alkyl (or hydrogen) with an ester group. For ynamides substituted with an electron‐rich phenyl group, their reactions with azidoalkenes proceed through novel 4+3 cycloadditions to deliver 1H‐benzodazepine products instead.
Completing the ring: Gold‐catalyzed cycloadditions of ynamides with azidoalkenes or 2H‐azirines give three distinct classes of 3+2 or 4+3 cycloadducts, depending on the types of the initial ynamides and 2H‐azirines (see scheme; EWG=electron‐withdrawing group).
Capturing volatile radionuclide iodine from nuclear and medical waste streams is an important environmental issue. In this work, we found that the 2,6-position hydrogen atoms of a BODIPY core undergo ...fast iodination with volatile iodine at room temperature. Inspired by our observation, two novel BODIPY-based conjugated porous polymers (CPPs) BDP-CPP-1 and BDP-CPP-2, and the reference compound NBDP-CPP, were prepared, which were designed and then synthesized via the Sonogashira cross-coupling reaction of 1,3,5-triethynyl-benzene (TEB) and dibromo-substituted derivatives. With the coexistence of the BODIPY units and plenty of triple bonds and phenyl rings that could adsorb iodine with high capacity and affinity, compounds BDP-CPP-1 and BDP-CPP-2 exhibited satisfactory iodine adsorption capacities of 2830 mg g-1 and 2230 mg g-1, respectively. Moreover, BDP-CPP-1 was shown to adsorb volatile iodine through a chemical mechanism involving the 2,6-position hydrogen atoms of the BODIPY core. Surprisingly, the active sites on the BODIPY units for a chemical iodination reaction were mostly eliminated as a result of the crosslinking of BODIPY units during the Sonogashira coupling reaction. The preliminary results demonstrated that the iodine uptake abilities, which are in the order of BDP-CPP-1 > BDP-CPP-2 > NBDP-CPP, are not only dependent on the surface area, but also on the BODIPY units. The BDP-CPPs show high thermal stability with a decomposition temperature of about 300 degree C. In addition, the BDP-CPPs demonstrated remarkable recyclability. Due to the highly pi -conjugated porous structure along with the high affinity for iodine molecules and iodination sites, some BODIPY-based CPPs may provide a feasible pathway to adsorb other volatile compounds.
A barely reached balance between weak intramolecular‐charge‐transfer (ICT) and small singlet–triplet splitting energy (ΔEST) for reverse intersystem crossing from non‐emissive triplet state to ...radiative singlet state impedes the realization of deep‐blue thermally activated delayed fluorescence (TADF) materials. By discarding the twisted‐ICT framework for a flattened molecular backbone and introducing a strong acceptor possessing n–π* transition character, hypsochromic color, a large radiative rate (kF), and small ΔEST are achieved simultaneously. Six molecules with a 9,9‐dimethyl‐10‐phenyl‐9,10‐dihydroacridine (i‐DMAc) donor are synthesized and investigated. Coinciding with time‐dependent density functional theory, the reduced dihedral angles between donor (D) and acceptor (A) weaken ICT from dispersed charge density and enable a large kF from increased frontier molecular orbitals overlap. Despite the separated highest occupied (HOMO) and lowest unoccupied molecular orbital (LUMO) population, the intercalation of phenyl bridges between D–A increases kF but significantly lowers the local triplet excited state, indicating small HOMO and LUMO overlap is not a sufficient, but necessary condition for reduced ΔEST. Integrating short conjugation length and carbonyl or triazine acceptors into the complanation molecules, deep‐blue TADF organic light‐emitting diodes demonstrate maximum external quantum efficiencies of 11.5% and 10.9% with Commission Internationale de l'Eclairage coordinates of (0.16, 0.09) and (0.15, 0.11), respectively, which is quite close to the stringent National Television System Committee blue standard.
Integrating a strong electron‐withdrawing acceptor moiety with short conjugation length and n–π* character into a planar molecular backbone is promising for meeting high radiative rate, weak intramolecular charge‐transfer state, and small singlet–triplet splitting energy simultaneously. Employing such a strategy, deep‐blue organic light emitting diode with external quantum efficiency of 11.5% and Commission Internationale de l'Eclairage coordinates of (0.16, 0.09) is achieved.
An unexpected route for the synthesis of N,N-dialkyl formamidines has been reported by the reaction of amines with N,N-dialkyl formamides and phenyl chloroformate.
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FeCl sub(3)-catalyzed aza-Prins-cyclization reaction of alpha -sulfonamido-allenes with aldehydes afforded 1,2,3,6-tetrahydropyridine or 2,5-dihydro-1H-pyrrole derivatives efficiently and highly ...selectively. The different regioselectivity is probably caused by the stabilizing effect of the phenyl group on the positively charged allylic intermediate.
Abstract The Pd‐catalysed decarboxylative asymmetric allylic alkylation (DAAA) of sterically hindered α‐aryl,β‐amido allyl ester lactams has been developed. The key step in the synthesis of a range ...of α‐aryl lactam substrates for catalysis was a Pb‐mediated α‐arylation of a β‐amido allyl ester affording 14 novel examples of α‐aryl‐β‐amido allyl ester lactams in good yields (up to 80 %). The Pd‐catalysed DAAA was optimised with the 2,4,6‐trimethoxyphenyl‐containing substrate. Using ( S , S )‐DACH‐phenyl Trost as the optimal chiral ligand, enantioselectivities of up to 82 % ee were obtained. A substrate scope of 11 examples of α‐aryl‐β‐amido allyl ester lactams showed that products containing the di‐ ortho ‐methoxy‐substituted phenyls and naphthyl groups gave rise to the highest ees, whereas products not bearing this substitution pattern showed lower enantioselectivities (<60 % ee ). Transition states to rationalise the observed stereochemical outcome are proposed.
To elucidate the impact of widely employed solubilizing phenoxy substituents on the structural and functional properties of perylene bisimide (PBI) dyes a series of 1,7-diphenoxy-substituted PBIs was ...prepared from 1,7-dibromo PBI which exhibit hydrogen, methyl, isopropyl or phenyl substituents at one or both orthopositions of the phenoxy substituents. Despite increasing sterical congestion high yields of 74-88% could be obtained for all twofold aromatic nucleophilic substitution reactions. The structural and optical properties in solution and in the solid state were investigated by super(1)H NMR, UV-Vis absorption and fluorescence spectroscopy, single crystal X-ray analyses (four structures) as well as quantum chemical and force field calculations. For the latter we used an adapted force field which correctly reflects the rigidity of the PBI core. Our studies show that these dyes prefer to accommodate a slightly twisted molecular structure in solution that is supported by CH...O hydrogen bonds between the 1,7-oxygen and the 6,12-hydrogen substituents. Because of the rather shallow potential energy surface, however, the molecules may planarize in the crystalline state under the influence of packing forces as revealed by single crystal X-ray analyses for two derivatives bearing methyl or phenyl substituents at all phenoxy ortho-positions. Such substituents are also suited to enwrap the PBI pi -scaffold and to prohibit PBI aggregation in the bulk state giving rise to defined vibronic progressions in the solid state UV-Vis absorption and emission spectra, and appreciable fluorescence quantum yields of up to 37%. In dichloromethane solution all of these 1,7-diphenoxy-substituted PBI dyes exhibit fluorescence quantum yields of 98-100% despite significant differences in the shape of the UV-Vis absorption band. The latter was explained in terms of rigidity because the molecules bearing four ortho-substituents at the phenoxy substituents were shown to prevail in much more fixed conformations compared to their more simple counterparts. Our findings underline that the conformational flexibility of bay-substituents can have an important impact on the functional properties of PBI dyes.
Seven new derivatives of phenanthro9,10-dimidazole having differenet substituents at the 1st and the 2nd positions of the phenanthroimidazole moiety were synthesized and characterized. The ...comparative study of their properties was performed employing thermal, optical, electrochemical and photoelectrical measurements. The properties of the newly synthesized compounds were compared with those of earlier reported derivatives of phenanthroimidazole and several interesting new findings were disclosed. Density functional theory calculations accompanied by optical spectroscopy measurements have shown the possibility of tuning the emission properties (excited-stated decay rate, fluorescence quantum yield, etc.) of phenanthro9,10-dimidazole derivatives via attachment of different substituents to the 1st and the 2nd positions. The most polar and bulky substituents linked to the 2nd position were found to have the greatest impact on the emissive properties of compounds causing (i) fluorescence quantum yield enhancement of dilute liquid and solid solutions (up to 97%), (ii) suppression of intramolecular torsion-induced nonradiative excited-state relaxation in rigid polymer films as well as (iii) inhibition of aggregation-promoted emission quenching in the neat films. Most of the studied compunds exhibited ambipolar charge transport character with comparable drift mobilities of holes and electrons. The highest hole and electron mobilities approaching 10
cm
V
s
were observed for the derivative having a triphenylamino group at the 1st position of the imidazole ring and the phenyl group at the 2nd position. The estimated triplet energies of phenanthro9,10-dimidazole compounds were found to be in the range of 2.4-2.6 eV, which is sufficiently high to ensure effective energy transfer to yellow/red emitters.
The manifold of reaction pathways for the oxidative addition of phenyl bromide and phenyl chloride substrates to phosphine-modified palladium(0) complexes has been investigated with ...dispersion-corrected density functional theory (B3LYP-D2) for a range of synthetically relevant ligands, permitting the evaluation of ligand, substrate and method effects on calculated predictions. Bulky and electron-rich ligands P(t)Bu3 and SPhos can access low-coordinate complexes more easily, facilitating formation of the catalytically active species throughout the cycle. While the bisphosphine oxidative addition step is reasonably facile for the smaller PCy3 and PPh3 ligands, the dissociation of these ligands to generate reactive palladium complexes becomes more important and the catalyst is more likely to become trapped in unreactive intermediates. This study demonstrates the feasibility of exploring the catalytic manifold for synthetically relevant ligands with computational chemistry, but also highlights the remaining challenges.
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