Dynamic effects on the nonlinear optical properties of donor acceptor stenhouse adducts: insights from combined MD + QM simulations.

The second-order nonlinear optical (NLO) responses of a donor-acceptor stenhouse adduct (DASA) are investigated by using a computational approach combining molecular dynamics simulations and density functional theory (DFT) calculations. Specific force fields for the open and closed photoswitching forms are first parameterized and validated according to the Joyce protocol, in order to finely reproduce the geometrical features and potential energy surfaces of both isomers in chloroform solution. Then, DFT calculations are performed on structural snapshots extracted at regular time steps of the MD trajectories to address the influence of the thermalized conformational dynamics on the NLO responses related to hyper-Rayleigh scattering (HRS) experiments. We show that accounting for the structural dynamics largely enhances the HRS hyperpolarizability (ßHRS) compared to DFT calculations considering solely equilibrium geometries, and greatly improves the agreement with experimental measurements. Furthermore, we show that the NLO responses of the NLO-active open form are correlated with the bond order alternation along the triene bridge connecting the donor and acceptor moieties, which is rationalized using simple essential state models.

Solvent and alkyl substitution effects on charge-transfer mediated triplet state generation in BODIPY dyads: a combined computational and experimental study.

Donor-acceptor dyads based on BODIPYs have been recently employed to enhance the formation of triplet excited states with the process of spin-orbit charge transfer intersystem crossing (SOCT-ISC) which does not require introduction of transition metals or other heavy atoms into the molecule. In this work we compare two donor-acceptor dyads based on meso-naphthalenyl BODIPY by combining experimental and computational investigations. The photophysical and electrochemical characterization reveals a significant effect of alkylation of the BODIPY core, disfavoring the SOCT-ISC mechanism for the ethylated BODIPY dyad. This is complemented with a computational investigation carried out to rationalize the influence of ethyl substituents and solvent effects on the electronic structure and efficiency of triplet state population via charge recombination (CR) from the photoinduced electron transfer (PeT) generated charge-transfer (CT) state. Time dependent-density functional theory (TD-DFT) calculations including solvent effects and spin-orbit coupling (SOC) calculations uncover the combined role played by solvent and alkyl substitution on the lateral positions of BODIPY.

Nonlinear Optical Responses of Photoswitchable Donor-Acceptor Stenhouse Adducts.

This work combines hyper-Rayleigh scattering (HRS) experiments performed in the NIR range (1.30 and 1.60 µm) and quantum chemical calculations to provide a comprehensive description of the second harmonic generation (SHG) responses of donor-acceptor Stenhouse adducts (DASAs). Representative derivatives of the three generations of DASAs, which differ by the nature of their electron-donating and withdrawing moieties and also include clickable species, have been synthesized and their photoswitching behavior fully characterized. The HRS measurements allow us to establish relationships between the magnitude of the SHG response of open forms and the nature of the donor and acceptor groups. The largest SHG responses are obtained for derivatives incorporating either a barbituric acid or an indanedione acceptor unit, while N-methylaniline appears as the most efficient donor group. The calculations support well the experimental data and show that high hyperpolarizabilities are associated to low excitation energies and large extent of the photoinduced intramolecular charge transfer, which enhances the dipole moment variation between the ground and first dipole-allowed electronic excited state. In addition, a complete investigation of the photoswitching kinetics of DASAs in chloroform solution shows important differences, highlighting in particular the role of the donor group on the photoswitching efficiency.

Validity and reliability of the Italian translation of the Yale Pharyngeal Residue Severity Rating Scale.

Objective: In the dysphagic patient, pharyngeal residues (PR) are associated with aspiration and poor quality of life. The assessment of PR using validated scales during flexible endoscopic evaluation of swallowing (FEES) is crucial for rehabilitation. This study aims to validate and test the reliability of the Italian version of the Yale Pharyngeal Residue Severity Rating Scale (IT-YPRSRS). The effects of training and experience in FEES on the scale were also determined. Methods: The original YPRSRS was translated into Italian according to standardised guidelines. Thirty FEES images were selected after consensus and proposed to 22 naive raters who were asked to assess the severity of PR in each image. Raters were divided into two subgroups by years of experience at FEES, and randomly by training. Construct validity, inter-rater, and intra-rater reliability were assessed by kappa statistics. Results: IT-YPRSRS showed substantial to almost perfect agreement (kappa > 0.75) in validity and reliability for both the overall sample (660 ratings), and valleculae/pyriform sinus sites (330 ratings each). No significant differences emerged between groups considering years of experience, and variable differences were observed by training. Conclusions: The IT-YPRSRS demonstrated excellent validity and reliability in identifying location and severity of PR.

Biofeedback as an Adjunctive Treatment for Post-stroke Dysphagia: A Pilot-Randomized Controlled Trial.

BACKGROUND AND PURPOSE: Post-stroke dysphagia affects almost half of the survivors and severely influences quality of life, thus becoming swallowing rehabilitation of paramount importance. However, there is little adequate evidence on which the best rehabilitative strategy can be. Surface electromyography (sEMG) allows for recording swallowing muscles' activity and provides real time visual feedback, as a biofeedback adjunctive technique to improve treatment outcome. This study aimed to analyze the effectiveness of biofeedback rehabilitation of swallowing through sEMG compared to standard techniques, in post-stroke dysphagia. METHODS: A pilot-randomized controlled trial included 17 patients diagnosed with post-stroke dysphagia. Nine underwent sEMG-biofeedback rehabilitation; seven controls were submitted to control treatment, one dropout. The primary outcome was the functional oral intake scale (FOIS), secondary outcomes was pharyngeal clearance and safe swallowing, assessed through fiberoptic endoscopic evaluation of swallowing (FEES). RESULTS: FOIS improved in all patients, regardless of treatment. sEMG-biofeedback rehabilitation led to improvements of the pharyngeal clearance and swallowing safety. The rehabilitative effects appeared stable at 2-months follow-up. CONCLUSIONS: The application of biofeedback based on sEMG in post-stroke dysphagia patients resulted in an effective rehabilitative technique, in particular for pharyngeal clearance improvements and safe swallowing, thus reducing the risk of aspiration and malnutrition.

New examples of Ru(II)-tetrazolato complexes as thiocyanate-free sensitizers for dye-sensitized solar cells.

A set of three new Ru(ii) polypyridyl complexes decorated with 5-aryl tetrazolato ligands (R-CN4)-, (D series, namely D1, D3 and D4), is presented herein. Whereas complex D1 represents the pyrazinyl tetrazolato analogue of a previously reported Ru(ii) complex (D2) with the general formula cis-[(dcbpy)2Ru(N^N)]+, in which dcbpy is 2,2'-bipyridine-4,4'-dicarboxylic acid and N^N is the chelating 2-pyridyl tetrazolato anion, the design of the unprecedented Ru(ii) species D3 and D4 relied upon a completely different architecture. More specifically, the molecular structure of thiocyanate-based species cis-[(dcbpy)2Ru(NCS)2], that is typically found in benchmark Ru(ii) dyes for dye sensitized solar cell (DSSCs), was modified with the replacement of two of the -NCS ligands in favour of the introduction of 5-aryl tetrazolato anions, such as the deprotonated form of 5-(4-bromophenyl)-1H-tetrazole, for complex D3 and 5-(4-cyanophenyl)-1H-tetrazole in the case of complex D4. To streamline the behavior of the D series of Ru(ii) complexes as photosensitizers for DSSCs, an in-depth analysis of the excited state properties of D1, D3 and D4 was performed through TDDFT calculations and TDAS (nanosecond transient difference absorption spectroscopy). The obtained results highlight a trend that was confirmed once D1, D3 and D4 were tested as photosensitizers for DSSC under different conditions. Along the series of the Ru(ii) complexes, the neutrally charged species D3 and D4 displayed the best photovoltaic performances.