ABSTRACT
We relate the chemical structure of a series of methyl (Me) substituted group III metal tris(8-quinolinolato) chelates (nMeq(3)M: n = 0, 3, 4, 5; M = Al(3+), Ga(3+)) to their photoluminescence (PL), electroluminescence, and thermal properties. Methylation of the 8-quinolinol ligand at the 3 or 4 position (pyridyl ring) results in a factor of 1.4 and 3.0 enhancement of PL quantum efficiency (phi(PL)), respectively, whereas methylation at the 5 position (phenoxide ring) results in a factor of approximately 3.0 decrease in phi(PL) relative to the unsubstituted analogue. Electroluminescent quantum efficiencies of undoped organic light-emitting devices using the aluminum tris(8-quinolinolato) chelates are 1, 0.45, 1.4, and 0.80% for unsubstituted 5-, 4-, and 3-methyl-8-quinolinol ligands, respectively. Devices made with the latter two ligands have a higher operating voltage to generate the same current density. Similar trends were observed for methylation of gallium tris(8-quinolinolato) chelates. We relate these results to the thermal properties of the compounds measured by simultaneous differential scanning calorimetry and thermal gravimetric analysis. The C-4 methylated derivatives exhibit approximately 60 degrees C lower crystalline melting points than all other derivatives, indicating the weakest cohesive forces between molecules. Unlike Alq(3), both the C-4 and C-5 methylated derivatives show no recrystallization of the glassy state below 500 degrees C and exhibit approximately 20-25 degrees C higher glass transition temperatures. We infer that methylation of the 8-quinolinol ligand reduces intermolecular interactions and consequently impedes charge transport through the film.
ABSTRACT
A discussion is provided of clinical techniques for establishing abstinence and preventing relapse in cocaine addicts within the context of an intensive outpatient treatment program. A basic tenet of this article is that to produce higher success rates in these and other drug-dependent patients more attention must be paid to some very fundamental treatment issues, such as program structure, counselor attitude, and patient motivation.
Subject(s)
Cocaine , Substance-Related Disorders/therapy , Female , Humans , Male , Motivation , Outpatients , Recurrence , Substance-Related Disorders/psychology , Substance-Related Disorders/urineABSTRACT
Faced with the difficult challenge of making effective treatment more available to larger numbers of addicts/users at lower cost, providers and payers of addiction/drug user treatment in the U.S. are looking for cost-effective models of outpatient care as alternatives to expensive residential treatment. This article discusses the clinical appropriateness of outpatient treatment and how to make it more efficacious for cocaine and crack addicts/users.