Vibrationally resolved absorption and emission spectra of rubrene multichromophores : temperature and aggregation effects

We present a theoretical study on the temperature-dependent absorption and photoluminescence spectroscopy of rubrene multichromophores by combining the time-dependent long-range-corrected density functional theory with the exciton model. The spectra of rubrene multichromophores up to heptamers are calculated, and the effects of exciton−phonon coupling and temperature on the photophysical properties of both H- and J-aggregated oligomers are addressed. It is found that the spectral behavior of rubrene aggregates is very much dependent on aggregation details. As the temperature increases, higher excitonic states become populated, and low-energy dark states in H-aggregated oligomers become observable gradually while the peak intensities near the 0−0 transition decrease for J-aggregated oligomers

Theoretical studies of vibrationally resolved absorption and emission spectra: From a single chromophore to multichromophoric oligomers/aggregates

National Natural Science Foundation of China [20673104, 20833003]; 973 project [2004CB719901, 2006CB922004]Absorption and photoluminescence spectroscopies are useful tools to study the photo-physical properties of materials. The theoretical methods for calculation of the spectra of molecules/supermolecules and aggregates, whose structures can differ significantly, are reviewed from the viewpoint of computational efficiency. Several model compounds/multimers are taken as examples for the spectral calculations. The numerical results achieve a satisfactory agreement between the theory and experiment

Investigating the Structural Origin of Trpzip2 Temperature Dependent Unfolding Fluorescence Line Shape Based on a Markov State Model Simulation

Vibrationally resolved fluorescence spectra of the beta-hairpin trpzip2 peptide at two temperatures as well as during a T-jump unfolding process are simulated on the basis of a combination of Markov state models and quantum chemistry schemes. The broad asymmetric spectral line shape feature is reproduced by considering the exciton-phonon couplings. The temperature dependent red shift observed in the experiment has been attributed to the state population changes of specific chromophores. Through further theoretical study, it is found that both the environment's electric field and the chromophores' geometry distortions are responsible for tryptophan fluorescence shift

Metformin versus insulin for the treatment of gestational diabetes

Background: Metformin is a logical treatment for women with gestational diabetes mellitus, but randomized trials to assess the efficacy and safety of its use for this condition are lacking. Methods: We randomly assigned 751 women with gestational diabetes mellitus at 20 to 33 weeks of gestation to open treatment with metformin (with supplemental insulin if required) or insulin. The primary outcome was a composite of neonatal hypoglycemia, respiratory distress, need for phototherapy, birth trauma, 5-minute Apgar score less than 7, or prematurity. The trial was designed to rule out a 33% increase (from 30% to 40%) in this composite outcome in infants of women treated with metformin as compared with those treated with insulin. Secondary outcomes included neonatal anthropometric measurements, maternal glycemic control, maternal hypertensive complications, postpartum glucose tolerance, and acceptability of treatment. Results: Of the 363 women assigned to metformin, 92.6% continued to receive metformin until delivery and 46.3% received supplemental insulin. The rate of the primary composite outcome was 32.0% in the group assigned to metformin and 32.2% in the insulin group (relative risk, 0.99; 95% confidence interval, 0.80 to 1.23). More women in the metformin group than in the insulin group stated that they would choose to receive their assigned treatment again (76.6% vs. 27.2%, P<0.001). The rates of other secondary outcomes did not differ significantly between the groups. There were no serious adverse events associated with the use of metformin. Conclusions: In women with gestational diabetes mellitus, metformin (alone or with supplemental insulin) is not associated with increased perinatal complications as compared with insulin. The women preferred metformin to insulin treatment. (Australian New Zealand Clinical Trials Registry number, 12605000311651.)Janet A. Rowan, William M. Hague, Wanzhen Gao, Malcolm R. Battin, M. Peter Moor