Directive influence of the keto bridge on the isomerization pathways of 2,3-dicarbonyl-2,3-diazanorbornen-7-one derivatives

The synthesis, electronic properties, and performance in dye-sensitized solar cells (DSSCs) of four cone-shaped organic dyes (ITD, ITD-Th, ITD-Hx, and ITD-OM) containing the isotruxene π-scaffold are reported. Selective substitution of the unsymmetrical isotruxene core with two diarylamino donors and one cyanocarboxylic acid acceptor was achieved by using a prefunctionalized dibromoisotruxene building block. The ortho-para-branched isotruxene core allows strong electronic couplings among the donors and the acceptor, leading to red-shifted absorption profiles with significant charge-transfer character. All four isotruxene dyes display reversible anodic waves in cyclic voltammagrams with both HOMO and LUMO potentials suitable for application in DSSCs. The DSSCs fabricated with these cone-shaped organic dyes exhibited high open-circuit voltages (0.67-0.76 V) and fill factors (0.67-0.72) with a power conversion efficiency (η) up to 5.45%, which is 80% of the ruthenium dye N719-based standard cell fabricated and measured under the same conditions.

show abstract

“…The synthesis of 1 was previously reported , and our melting points and 1 H NMR spectrum conform to the literature data.…”

Section: Methodssupporting

confidence: 75%

Isotruxene-Derived Cone-Shaped Organic Dyes for Dye-Sensitized Solar Cells

et al. 2010

View full text Add to dashboard Cite

show abstract

“…The n.m.r. absorptions of the methylene protons in its remaining ester group were widely separated, one at 5.96 and the other, highly shielded, at 6.55 r, an effect observed for the corresponding ester group in 4b as previously noted (2). Isomerization of l a was complete in the time (-30 s) taken to dissolve a sample in TFA in an n.m.r.…”

supporting

confidence: 73%

Isomerization of Bicyclic Hydrazine Monoesters to N-Amino-2-pyridone Esters, Precursors to Bicyclic "Isosydnones"

Mackay¹,

Wong²

1975

Can. J. Chem.

Self Cite

View full text Add to dashboard Cite

DONALD MACKAY and LICHIN L. WONG. Can. J. Chem. 53,1973Chem. 53, (1975. Selective aqueous alkaline hydrolysis of the diazetidine diesters 4 gives the basic monoesters 1 which isomerize quantitatively in trifluoroacetic acid or by refluxing with sodium methoxide in dioxane to the N-aminopyridone esters 2. The bridged pyridazine ester 5a can also be selectively hydrolyzed to the presumed intermediate 10, hydrolysis being accompanied by immediate isomerization to 2a. A common mechanistic pattern is proposed for these isomerizations.Heating of 2 causes loss of alcohol to give the mesoionic "isosydnone" 3, a fairly stable ring system slowly opened by ethanol to 2b and by concentrated alkali to the N-aminopyridone 16a. Oxidation of 16a with lead tetraacetate gives the pyridone 18a.DONALD MACKAY et LICHIN L. WONG. Can. J. Chem. 53,1973Chem. 53, (1975. L'hydrolyse alkaline aqueuse selective des diesters de diazetidine 4 conduit au monoester basique 1 qui s'isomerise quantitativernent en ester de N-aminopyridone 2 lorsqu'on le traite par de l'acide trifluoroacetique ou par reflux en presence de methylate de sodium dans le dioxanne. L'ester cyclise de pyridazine 5a peut aussi Ctre hydrolyse sklectivement pour conduire a I'intermkdiaire presume 10; I'hydrolyse est accompagnke par une isomtrisation immediate en 2a. On suggere que ces isomerisations precedent par un mecanisme commun.Le chauffage de 2 conduit a une perte d'alcool fournissant "l'isosydnone" mesoionique 3, un systeme cyclique relativement stable, ouvert lentement par l'ethanol pour conduire a 2b et par les bases concentrees pour conduire a la N-aminopyridone 16a. L'oxydation de 16a par le tetraaktate de plomb conduit a la pyridone 18a. [Traduit par le journal]We have recently reported that an excess of trifluoroacetic acid (TFA) isomerizes the basic diazetidine ester l a to the aminopyridone ester 2a which cyclizes with loss of methanol to the mesoionic structure 3 (1).We now wish to describe some aspects of the chemistry of these ring systems and in particular to show that the esters 2 can be obtained under other quite different reaction conditions, again involving deep seated skeletal rearrangements.The diesters 4, the precursors to 1, were readily available in quantity as the end products of the thermal isomerization of the adducts 5 of azo esters with 2,5-dimethyl-3,4-diphenylcyclopentadienone (2). Though they are very stable to heat we have already shown that 4a is labile to acid, TFA causing demethylation and rearrangement to 6 (3). We were interested in trying to prepare the parent nitrogen unsubstituted 1,2-diazetidine 7, since examples of such diazetidines are unknown.Under varying conditions of alkaline hydrolysis it was found that one ester group in 4a was always easily removed. The product l a was unstable to prolonged exposure to the hydrolysis conditions especially at high temperature or with high alkali concentration but when it was allowed to react completely'the major end product was not the expected 7, but the dimer of the cyclone 2,5-dimeth...

show abstract

“…These results suggest that fragmentation probably occurs through nitrogen activation. Mechanisms involving both a [3,3]-sigmatropic rearrangement 14 or the stepwise trapping of an intermediate allylic cation have been proposed for similar transformations . In our case, the detection by MS of dimeric structures coming from the collapse of two ionic species indicates that a dissociative pathway takes place.…”

supporting

confidence: 54%