"Click-switch" - one-step conversion of organic azides into photochromic diarylethenes for the generation of light-controlled systems.

Diarylethenes (DAEs) are an established class of photochromic molecules, but their effective incorporation into pre-existing targets is synthetically difficult. Here we describe a new class of DAEs in which one of the aryl rings is a 1,2,3-triazole that is formed by "click" chemistry between an azide on the target and a matching alkyne-cyclopentene-thiophene component. This late-stage zero-length linking allows for tight integration of the DAE with the target, thereby increasing the chances for photomodulation of target functions. Nineteen different DAEs were synthesized and their properties investigated. All showed photochromism. Electron-withdrawing groups, and in particular -M-substituents at the triazole and/or thiophene moiety resulted in DAEs with high photo- and thermostability. Further, the chemical nature of the cyclopentene bridge had a strong influence on the behaviour upon UV light irradiation. Incorporation of perfluorinated cyclopentene led to compounds with high photo- and thermostability, but the reversible photochromic reaction was restricted to halogenated solvents. Compounds containing the perhydrogenated cyclopentene bridge, on the other hand, allowed the reversible photochromic reaction in a wide range of solvents, but had on average lower photo- and thermostabilities. The combination of the perhydrocyclopentene bridge and electron-withdrawing groups resulted in a DAE with improved photostability and no solvent restriction. Quantum chemical calculations helped to identify the photoproducts formed in halogenated as well as non-halogenated solvents. For two optimized DAE photoswitches, photostationary state composition and reaction quantum yields were determined. These data revealed efficient photochemical ring closure and opening. We envision applications of these new photochromic diarylethenes in photonics, nanotechnology, photobiology, photopharmacology and materials science.

Benchmark of the Extension of Frozen-Density Embedding Theory to Nonvariational Correlated Methods: The Embedded-MP2 Case.

The extension of the frozen-density embedding theory for nonvariational methods [J. Chem. Theory Comput. 2020, 16, 6880] was utilized to evaluate intermolecular interaction energies for complexes in the Zhao-Truhlar basis set. In the applied method (FDET-MP2-FAT-LDA), the same auxiliary system is used to evaluate the correlation energy by means of the second-order Møller-Plesset perturbation theory (MP2), as in our previous work [J. Chem. Phys. 2019, 150, 121101]. Local density approximation is used for ExcTnad[ρA,ρB] in both cases. Additionally, the contribution to the energy due to the neglected correlation potential was evaluated and analyzed. The domain of applicability of the local density approximation for ExcTnad[ρA,ρB] was determined based on deviations from the interaction energies from the conventional MP2 calculations. The local density approximation for ExcTnad[ρA,ρB] performs well for hydrogen- or dipole-bound complexes. The relative errors in the interaction energy lie within 3-30%. While for charge-transfer complexes, this approximation fails consistently, and for other types of complexes, the performance of this approximation is not systematic. The sources of error are discussed in detail.

Algebraic diagrammatic construction for the polarisation propagator in combination with effective fragment potentials.

The effective fragment potential (EFP) method for the efficient inclusion of solvation effects is combined with the algebraic diagrammatic construction (ADC) scheme for the second- and third-order polarisation propagator. The accuracy of these newly developed EFP-ADC(2) and EFP-ADC(3) methods is tested with respect to supermolecular ADC calculations for a selected set of small solute·solvent complexes. The EFP model for solvation introduces only marginal errors in the excitation energies and oscillator strengths of singlet as well as triplet states, which are strictly localized on the chromophore, significantly below the intrinsic errors of the parent ADC(2) and ADC(3) methods. It is only when delocalization of electron density on the solvent molecules occurs that the error in the excitation energies increases, a well-known behavior of environment models in general. Overall, EFP-ADC schemes prove to be reliable computational approaches to simulate electronic absorption spectra in solution.

The World Report on Disability and communication disability: some considerations from an Indian context.

The aim of this paper is to reflect and comment on the lead article by Wylie, McAllister, Davidson, and Marshall (2013) with reference to people with communication disability in India and illustrated by the work of one Indian non-governmental organization. Key themes and questions from Wylie et al. are identified and discussed. Suggestions for how the recommendations of the World Report on Disability might be implemented in an Indian context are made, notwithstanding the magnitude and scale of the demand for services in the context of the vast population. Nine recommendations at the meso- and micro-level are included. These emphasize three major themes: methodologies to ensure access for all those who need speech-language pathology services; enhancement of speech-language pathology training capacities to deliver holistic professional services in urban and rural settings; promotion of the involvement of advocacy groups in policy-making and, hence, facilitating people with communication needs to be more assertive about rights and entitlement.

Twelve tips for effective international clinical placements.

As universities adopt an increasingly international focus, student health professionals are keen to gain clinical experiences in other countries. Such clinical placements provide students with the opportunity to share their knowledge and at the same time acquire new clinical and cultural skills. The experience gained will not only enhance their clinical practice overseas, but will also enhance it in their home country where they are likely to work with people from culturally, linguistically and clinically diverse backgrounds. Careful preparation and adequate supports are critical if students and the host institutions are to gain maximum benefit from cross-cultural clinical placements. The tips below are based on an ongoing collaboration between the Indian Institute of Cerebral Palsy, Kolkata, India and The University of Sydney, as well as recommendations from the burgeoning literature on international clinical placements. The authors are from both the sending and the receiving institutions, and have found that close collaboration between the home and host institutions along with student reflection, evaluation and the opportunity to integrate new knowledge with other clinical experiences are keys to a satisfactory outcome for all concerned.