Binding Energy of Triplet Excitons in Nonfullerene Acceptors: The Effects of Fluorination and Chlorination.

One strategy to improve the photovoltaic properties of nonfullerene acceptors (NFAs), employed in state-of-art organic solar cells, is the rational fluorination or chlorination of these molecules. Although this modification improves important acceptor properties, little is known about the effects on the triplet states. Here, we combine the polarizable continuum model with an optimally tuned range-separated hybrid functional to investigate this issue. We find that fluorination or chlorination of NFAs decreases the degree of the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) overlap along these molecules. Consequently, the energy gap between T1 and S1 states, ΔEST = ES1 - ET1, also decreases. This effect reduces the binding energy of triplet excitons, which favors their dissociation into free charges. Furthermore, the reduction of ΔEST can contribute to mitigating the losses produced by the nonradiative deactivation of the T1 excitons. Interestingly, although Cl has a lower electronegativity than F, chlorination is more effective to reduce ΔEST. Since the chlorination of NFAs is easier than fluorination, Cl substitution can be a useful approach to enhance solar energy harvesting using triplet excitons.

Electrochemically deposited poly(3-methylthiophene) performance in single layer photovoltaic devices.

Photovoltaic devices based on electrochemically synthesized poly(3-methylthiophene) PMeT were constructed and characterized. The charge mobility for positive carriers of this polymer is quite high, 4 x 10(-4) cm2/Vs, being attractive for optoelectronic devices. In single layer photovoltaic devices with PMeT active layer electrochemically deposited onto indium-tin oxide substrate with aluminum as top electrode we have obtained short-circuit current density of 0.31 A/m2, open-circuit voltage of 1 V and power conversion efficiency of 0.14% at 100 W/m2 white light irradiance.

Effects of P5, a novel oxazolo(3,2-a)pyridine derivative with a long-acting antihypertensive activity, on different agonist-mediated pressor responses in pithed rats.

1. An oxazolo(3,2-a)pyridine derivative P5, described chemically as (+/-)-ethyl-7-(3-nitrophenyl)-5,8a-dimethyl-6-methoxycarbonyl-2,3,8,8a-tetrahydro-7H-oxazolo[3,2-a]pyridin-8-carboxylate, is a novel compound that has been synthesized as a possible antihypertensive prodrug of the 1,4-dihydropyridine type. Its antihypertensive activity was described in a previous study by the authors (Morán, Martin, Velasco, Martin, San Roman, Caballero, Puebla, Medarde & San Feliciano, 1997). 2. The aim of this work was to establish in vivo, the possible mechanisms participating in this antihypertensive action. Accordingly, we examined the effect of P5 on the pressor responses induced in pithed rats by noradrenaline (an alpha1-, alpha2- and beta-adrenoceptor agonist), xylazine (an alpha2-adrenoceptor agonist), methoxamine (an alpha1-adrenoceptor agonist), angiotensin I, angiotensin II, L-NAME (a nitric oxide synthase inhibitor) and BayK 8644 (a calcium channel agonist) and compared them with those of nifedipine, used as the reference drug. 3 Intravenous (i.v.) administration of P5 (2.5-10 mg kg(-1)) inhibited the pressor responses to noradrenaline (1 microg kg(-1)), xylazine (80 microg kg(-1)), angiotensin I (0.5 microg kg(-1)), angiotensin II (0.5 microg kg(-1)), BayK 8644 (30 microg kg(-1)) and L-NAME (10 mg kg(-1)). Nifedipine (10 microg kg(-1), i.v.) reduced the pressor responses to all these agonists and also to methoxamine (2 microg kg(-1)). 4. However, P5 was more effective than nifedipine in inhibiting these responses and its inhibitory effect lasted longer. Intravenous infusion of calcium gluconate (1 ml kg(-1) min(-1)) reversed the reduction in the pressor responses as a result of nifedipine. The effects of P5 were only reversed at 2-3 h after administration. 5 These results suggest that P5 has a strong capacity to inhibit the pressor responses to several agonists after its i.v. administration and that such effects are related to its potent antihypertensive activity.

Insecticidal neolignans from Piper decurrens.

2,3-Dihydro-2-(4'-hydroxyphenyl)-3-methyl-5(E)-propenylbenzofuran (conocarpan) (1), 2-(4'-hydroxy-3'-methoxyphenyl)-3-methyl-5(E)- propenylbenzofuran (eupomatenoid-5) (2), and 2-(4'- hydroxyphenyl)-3-methyl-5(E)-propenylbenzofuran (eupomatenoid-6) (3), three known neolignans found for the first time in a species of the Piperaceae, were isolated from Piper decurrens via insecticidal bioassay-guided fractionation, along with a small quantity of a new related compound, 2,3-dihydro-5-formyl-2-(4'-hydroxyphenyl)-3-methylbenzofuran (decurrenal) (4), and 3,7,11,15-tetramethyl-2(E)-hexadecen-1-ol (trans-phytol).

MR-14134, a new benzothiazepine with central hypotensive action.

Structural changes introduced into the benzothiazepine molecule have led to a compound, MR-14134 (3-[(3-dimethylamino)propyl]-2,3,4,5- tetrahydro-2[4-methoxyphenyl]-1,5-benzothiazepin-4-one oxalate). We have compared the effects of MR-14134 and diltiazem on blood pressure and heart rate in anaesthetized and pithed rats following intravenous administration as well as in anaesthetized rats after intracerebroventricular administration and on the binding of [3H]clonidine in the rat cerebral cortex. MR-14134 (0.1-5.0 mg/kg, i.v.) produced a dose-dependent hypotensive and bradycardic effect similar in intensity but lasting longer than that of diltiazem. These effects were antagonized by previous administration of yohimbine but not by atropine, propranolol or ICI 118,551. Doses of 1 mg/kg i.v. of MR-14134 did not modify either blood pressure or heart rate in pithed rats and did not affect the hypertensive response elicited by electrical sympathetic stimulation or by exogenous administration of norepinephrine in pithed rats. Intracerebroventricular administration of MR-14134 (60 micrograms/kg) decreased blood pressure and heart rate in rats. This effect was antagonized by yohimbine and prazosin. [3H]Clonidine-binding experiments in the rat cortex showed that neither MR-14134 nor diltiazem have affinity for alpha 2A-adrenoceptors. These results confirmed that MR-14134 has a hypotensive and bradycardic effect in which, unlike diltiazem, the central nervous system is involved. These effects were mediated, at least partly, by alpha 2B-adrenoceptors and I1 imidazoline receptors.

JB-9322, a new selective histamine H2-receptor antagonist with potent gastric mucosal protective properties.

1. JB-9322 is a selective histamine H2-receptor antagonist with gastric antisecretory activity and mucosal protective properties. 2. The affinity of JB-9322 for the guinea-pig atria histamine H2-receptor was approximately 2 times greater than that of ranitidine. 3. In vivo, the ID50 value for the inhibition of gastric acid secretion in pylorus-ligated rats was 5.28 mg kg-1 intraperitoneally. JB-9322 also dose-dependently inhibited gastric juice volume and pepsin secretion. In gastric lumen-perfused rats, intravenous injection of JB-9322 dose-dependently reduced histamine-, pentagastrin- and carbachol-stimulated gastric acid secretion. 4. JB-9322 showed antiulcer activity against aspirin and indomethacin-induced gastric lesions and was more potent than ranitidine. 5. JB-9322 effectively inhibited macroscopic gastric haemorrhagic lesions induced by ethanol. Intraperitoneal injection was effective in preventing the lesions as well as oral treatment. The oral ID50 value for these lesions was 1.33 mg kg-1. By contrast, ranitidine (50 mg kg-1) failed to reduce these lesions. In addition, the protective effect of JB-9322 was independent of prostaglandin synthesis. 6. These results indicate that JB-9322 is a new antiulcer drug that exerts a potent cytoprotective effect in addition to its gastric antisecretory activity.