Asymmetric rotations and dimerization driven by normal to modulated phase transition in 4-biphenylcarboxy coupled L-phenylalaninate

Amongst the derivatives of 4-biphenylcarboxylic acid and amino acid esters, the crystal structure of 4-biphenylcarboxy-(L)-phenylalaninate is unusual owing to its monoclinic symmetry within a pseudo-orthorhombic lattice. The distortion is described by disparate rotational property around the chiral centers ($\varphi_{\mathrm{chiral}}$ $\simeq$ -129 degrees and 58 degrees) of the two molecules in the asymmetric unit. Each of these molecules comprise of planar biphenyl moieties ($\varphi_{\mathrm{biphenyl}}$ = 0 degrees). Using temperature dependent single crystal X-ray diffraction experiments we show that the compound undergoes a phase transition below $T$ $\sim$ 124 K that is characterized by a commensurate modulation wave vector, $\mathbf{q}$ = $\delta(101)$, $\delta$ = $\frac{1}{2}$. The (3+1) dimensional modulated structure at $T$ = 100 K suggests that the phase transition drives the biphenyl moieties towards non coplanar conformations with significant variation of internal torsion ($\varphi^{\mathrm{max}}_{\mathrm{biphenyl}}$ $\leq$ $20$ degrees). These intramolecular rotations lead to dimerization of the molecular stacks that are described predominantly by intermolecular tilts and small variations in intermolecular distances. Atypical of modulated structures and superstructures of biphenyl and other polyphenyls, the rotations of individual molecules are asymmetric ($\Delta$$\varphi_{\mathrm{biphenyl}}$ $\approx$ 5 degrees) while $\varphi_{\mathrm{biphenyl}}$ of one independent molecule is two to four times larger than the other. Crystal-chemical analysis and phase relations in superspace suggest multiple competing factors involving intramolecular steric factors, intermolecular H--C${\cdot}{\cdot}{\cdot}$C--H contacts and weak C--H${\cdot}{\cdot}{\cdot}$O hydrogen bonds that govern the distinctively unequal torsional property of the molecules

Generate, Repurpose, Validate: A Receptor-Mediated Atom-by-Atom Drug Generation for SARS-Cov-2 Spike Protein and Similarity-Mapped Drug Repurposing for COVID-19 with Rigorous Free Energy Validation Using Well-Tempered Metadynamics

Finding a cure for Covid-19 is of immediate and paramount importance. In this study, we propose new and repurpose drugs to prevent SARS-Cov-2 (Covid-19) viral attack on human cells. Our study comprises three steps: generation of new molecules, structural similarity mapping to existing approved and investigational drugs, and validation of their binding strengths to the viral spike proteins based on rigorous all-atom well-tempered metadynamics free energy calculations. We show that some of our new molecules and some of the existing drugs bind more strongly than human ACE2 protein to the viral spike protein. Therefore, these drug molecules may have the potential to be repurposed as a preventive therapy for Covid-19, subject to further experimental verifications

Engineering Soluble Diketopyrrolopyrrole Chromophore Stacks from a Series of Pd(II)‐based Ravels

Funder: Studienstiftung des Deutschen Volkes; doi: http://dx.doi.org/10.13039/501100004350Funder: Winton Programme for the Physics of SustainabilityFunder: Rowland Institute at Harvard; doi: http://dx.doi.org/10.13039/100009835A strategy to engineer the stacking of diketopyrropyrrole (DPP) dyes based on non‐statistical metallosupramolecular self‐assembly is introduced. Therefore, the DPP backbone is equipped with nitrogen‐based donors that allow for different discrete assemblies to be formed upon addition of Pd(II), distinguished by the number of π‐stacked chromophores. A Pd3L6 three‐ring, a heteroleptic Pd2L2L’2 ravel composed of two crossing DPPs (flanked by two carbazoles), and two unprecedented self‐penetrated motifs (a Pd2L3 triple and a Pd2L4 quadruple stack), were obtained and systematically investigated. With increasing counts of stacked chromophores, UV‐Vis absorptions red‐shift and emission intensities decrease, except for compound Pd2L2L’2 which stands out with an exceptional photoluminescence quantum yield of 52%. This is extraordinary for open‐shell metal containing assemblies and explainable by an intra‐assembly FRET process. The modular design and synthesis of soluble multi‐chromophore building blocks opens potential for the preparation of nanodevices and materials with applications in sensing, photo‐redox catalysis and optics.</jats:p

Engineering Soluble Diketopyrrolopyrrole Chromophore Stacks from a Series of Pd(II)‐Based Ravels**

A strategy to engineer the stacking of diketopyrrolopyrrole (DPP) dyes based on non-statistical metallosupramolecular self-assembly is introduced. For this, the DPP backbone is equipped with nitrogen-based donors that allow for different discrete assemblies to be formed upon the addition of Pd(II), distinguished by the number of π-stacked chromophores. A Pd$_3$L$_6$ three-ring, a heteroleptic Pd$_2$L$_2$L′$_2$ ravel composed of two crossing DPPs (flanked by two carbazoles), and two unprecedented self-penetrated motifs (a Pd$_2$L$_3$ triple and a Pd$_2$L$_4$ quadruple stack), were obtained and systematically investigated. With increasing counts of stacked chromophores, UV/Vis absorptions red-shift and emission intensities decrease, except for compound Pd$_2$L$_2$L′$_2$, which stands out with an exceptional photoluminescence quantum yield of 51 %. This is extraordinary for open-shell metal containing assemblies and explainable by an intra-assembly FRET process. The modular design and synthesis of soluble multi-chromophore building blocks offers the potential for the preparation of nanodevices and materials with applications in sensing, photo-redox catalysis and optics

Metal-like Ductility in Organic Plastic Crystals: Role of Molecular Shape and Dihydrogen Bonding Interactions in Aminoboranes

Ductility, which is a common phenomenon in most metals and metal-based alloys, is hard to achieve in molecular crystals. Organic crystals have been recently shown to deform plastically, but only on one or two faces, and fracture when stressed in any other arbitrary direction. Here, we report an exceptional metal-like ductility in crystals of two globular molecules, BH3NMe3 and BF3NMe3, with characteristic stretching, necking and thinning with deformations as large as ~ 500%. Surprisingly, the mechanically deformed samples not only retained good long range order, but also allowed structure determination by single crystal X-ray diffraction. Molecules in these high symmetry crystals interact predominantly via electrostatic forces (B––N+) and form columnar structures, thus forming multiple slip planes with weak dispersive forces among columns. While the former interactions hold molecules together, the latter facilitate exceptional malleability. On the other hand, the limited number of facile slip planes and strong dihydrogen bonding in BH3NHMe2 negates ductility. We show the possibility to simultaneously achieve both exceptional ductility and crystallinity in solids of certain globular molecules, which may enable designing highly modular, easy-to-cast crystalline functional organics, for applications in barocalorimetry, ferroelectrics and soft-robotics

Engineering Soluble Diketopyrrolopyrrole Chromophore Stacks from a Series of Pd(II)-Based Ravels.

Funder: Studienstiftung des Deutschen Volkes; doi: http://dx.doi.org/10.13039/501100004350Funder: Winton Programme for the Physics of SustainabilityFunder: Rowland Institute at Harvard; doi: http://dx.doi.org/10.13039/100009835A strategy to engineer the stacking of diketopyrrolopyrrole (DPP) dyes based on non-statistical metallosupramolecular self-assembly is introduced. For this, the DPP backbone is equipped with nitrogen-based donors that allow for different discrete assemblies to be formed upon the addition of Pd(II), distinguished by the number of π-stacked chromophores. A Pd3 L6 three-ring, a heteroleptic Pd2 L2 L'2 ravel composed of two crossing DPPs (flanked by two carbazoles), and two unprecedented self-penetrated motifs (a Pd2 L3 triple and a Pd2 L4 quadruple stack), were obtained and systematically investigated. With increasing counts of stacked chromophores, UV/Vis absorptions red-shift and emission intensities decrease, except for compound Pd2 L2 L'2 , which stands out with an exceptional photoluminescence quantum yield of 51 %. This is extraordinary for open-shell metal containing assemblies and explainable by an intra-assembly FRET process. The modular design and synthesis of soluble multi-chromophore building blocks offers the potential for the preparation of nanodevices and materials with applications in sensing, photo-redox catalysis and optics

Research data supporting "Mesitylated trityl radicals, a platform for doublet emission: symmetry breaking, charge-transfer states and conjugated polymers"

Compressed (.zip) folder containing data from normalized photoluminescence spectra of M3TTM and M2TTM-3PCz radicals and PFMTTM polyradical in 0.1 mM toluene solutions (Fig1c.xlsx); normalized steady-state emission spectra of MxTTM radicals in 0.1 mM toluene solutions (Fig3a.xlsx) and emission kinetics in the 580-610 nm region showing rapid emission following 520 nm excitation (Fig3b.xlsx); normalized steady-state emission spectra of MxTTM radicals in 8 wt% evaporated films in CBP showing increasing emission red-shift and linewidth broadening with decreasing mesitylation (Fig.3c.xlsx) and total emission kinetics in the range of 550-880 nm following 520 nm excitation using 100 fs pulses with fluence 5 μJ cm-2 (Fig3d.xlsx), inset shows early time kinetics (Fig3dInset.xlsx); time-gated photoluminescence spectra of 8 wt% M2TTM radical in CBP film showing monomer emission at nanosecond times and exciplex emission at microsecond times (Fig3e.xlsx); dynamics of emission of MxTTM radicals in CBP films showing time dependence of peak emission wavelength (Fig3f1.xlsx) and integrated photoluminescence counts in the range of 550-880 nm (Fig3f2.xlsx); external quantum efficiency versus current density (Fig4b.xlsx) and current density-voltage-luminance characteristics of organic light-emitting diodes with M2TTM-3PCz radical as the emitter (Fig4c.xlsx); normalized photoluminescence spectrum of the light-emitting layer of 5 wt% M2TTM-3PCz doped CBP film following 405 nm excitation and normalized electroluminescence spectrum of the device at 0.2 mA cm-2 (Fig4d.xlsx); computational atomic coordinates of optimized MxTTM structures in the ground and excited states calculated at the UB3LYP(D3)/def2-SVP and UCAM-B3LYP(D3)/def2-SVP levels of theory, respectively (MxTTM_coordinates.docx).This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreements No. 891167, No. 859752 and No. 886066, from the European Research Council under the European Union’s Horizon 2020 research and innovation programme grant agreement No. 101020167 and from the Engineering and Physical Sciences Research Council NanoDTC, EP/S003126/1, EP/S022953/1

Autonomous self-healing organic crystals for nonlinear optics.

Non-centrosymmetric molecular crystals have a plethora of applications, such as piezoelectric transducers, energy storage and nonlinear optical materials owing to their unique structural order which is absent in other synthetic materials. As most crystals are brittle, their efficiency declines upon prolonged usage due to fatigue or catastrophic failure, limiting their utilities. Some natural substances, like bone, enamel, leaf and skin, function efficiently, last a life-time, thanks to their inherent self-healing nature. Therefore, incorporating self-healing ability in crystalline materials will greatly broaden their scope. Here, we report single crystals of a dibenzoate derivative, capable of self-healing within milliseconds via autonomous actuation. Systematic quantitative experiments reveal the limit of mechanical forces that the self-healing crystals can withstand. As a proof-of-concept, we also demonstrate that our self-healed crystals can retain their second harmonic generation (SHG) with high efficiency. Kinematic analysis of the actuation in our system also revealed its impressive performance parameters, and shows actuation response times in the millisecond range