We have discovered two stericly hindered green coumarin derivatives which showed significantly better thermal stability and overall electroluminescence (EL) performance than those of the corresponding 3-(2-benzothiazolyl)-7-(diethylamino)-2H-1-benzopyran-2-one (C-6) and 10-(2-benzothiazolyl)-1,1,7,7-tetramethyl- 2,3,6,7-tetrahydro-1H,5H,11H-benzo[l]pyrano[6,7, 8-ij] quinolizin-11-one (C-545T). The strategic incorporation of bulky spacer t-butyl groups in these dopants considerably delays the onset of concentration quenching. In particular, 10-[2(5,7-di-t-butyl)benzothiazolyl]-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-benzo-[l]pyrano[6,7,8-ij]quinolizin-11-one (C-545TB) with its superb thermal stability (Tg=142 °C; Td=327 °C), high luminance efficiency (∼13 cd/A), good Commission Interationale d’Eclairage (CIE) coordinates (x=0.30; y=0.64) and a nearly flat EL efficiency dependence on drive current stands out as one of the best choice of green dopants for use in the passive-matrix organic light-emitting diode displays.

General Information: All reactions were performed under nitrogen. Solvents were carefully dried and distilled from appropriate drying agents prior to use. Commercially available reagents were used without further purification unless otherwise stated. All reactions were monitored by thin-layer chromatography (TLC) with Merck pre-coated glass plates. Flash column chromatography and preparative TLC were carried out using silica gel from Merck (230-400 mesh). Fast atom bombardment (FAB) mass spectra were recorded on a Finnigan MAT SSQ710 system. Proton NMR spectra were Ferrocene was added as a calibrant after each set of measurements, and all potentials reported were quoted with reference to the ferrocene-ferrocenium (Fc/Fc + ) couple at a scan rate of 100 mV s −1 .Thermal analyses were performed with the Perkin-Elmer TGA6 thermal analyzer.

The goal of this study is to investigate associations between subjective memory complaint and objective cognitive performance in older people with previous major depression–a high-risk sample for cognitive impairment and later dementia. A cross-sectional study was carried out in people aged 60 or over with previous major depression but not fulfilling current major depression criteria according to DSM-IV-TR. People with dementia or Mini-Mental State Examination score less than 17 were excluded. Subjective memory complaint was defined on the basis of a score ≧4 on the subscale of Geriatric Mental State schedule, a maximum score of 8. Older people aged equal or over 60 without any psychiatric diagnosis were enrolled as healthy controls. Cognitive function was evaluated using a series of cognitive tests assessing verbal memory, attention/speed, visuospatial function, verbal fluency, and cognitive flexibility in all participants. One hundred and thirteen older people with previous major depression and forty-six healthy controls were enrolled. Subjective memory complaint was present in more than half of the participants with depression history (55.8%). Among those with major depression history, subjective memory complaint was associated with lower total immediate recall and delayed verbal recall scores after adjustment. The associations between subjective memory complaint and worse memory performance were stronger in participants with lower depressive symptoms (Hamilton Depression Rating Scale score<7). The results suggest subjective memory complaint may be a valid appraisal of memory performance in older people with previous major depression and consideration should be given to more proactive assessment and follow-up in these clinical samples.

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