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Síntese de sistemas híbridos dicetopirrolopirrole-mediador redox para DSSCs
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Atualmente, as células solares sensibilizadas por corantes (DSSC) têm sido alvo de intensa investigação em vários grupos de investigação devido às vantagens que este modelo oferece em comparação com as células solares tradicionais. Entre essas vantagens estão o menor custo, maior flexibilidade e sustentabilidade. Um dos campos mais estudados nessa área é a criação de novos corantes orgânicos para atuarem como sensibilizadores, devido à diversidade de estruturas que podem ser idealizadas e desenvolvidas.
O esqueleto de dicetopirrolopirrole (DPP) em particular tem demonstrando muito potencial, graças à facilidade de introdução de substituintes, particularmente nos anéis aromáticos e grupos amida. Outro fator de realce, é a recente utilização de líquidos iónicos à base de 2,3-dimetilimidazólios como aditivo em eletrólitos, aumentar o rendimento de conversão energética. Este facto levou à idealização e síntese de novos dicetopirrolopirroles, com estrutura D-π-A (Doador-π-Aceitador), integrados com grupos carregados positiva e negativamente (2,3 dimetilimidizólio e sulfonato).
Para a introdução das unidades iónicas foram delineadas duas aproximações: i) a introdução destas unidades na cadeia alquilo presente no azoto do anel lactama do DPP e, ii) a introdução das mesmas unidades na parte doadora na estrutura.
Foi primeiramente sintetizado o núcleo do DPP substituído por grupos 4-bromofenil e 2-furanil, sendo esta estrutura utilizada como ponte conjugada (π) nos corantes posteriormente sintetizados. No primeiro caso e de modo a poder proceder à introdução da unidade iónica foi necessário a N-alquilação do átomo de azoto com (2-iodoetoxi)triisopropilsilano (R10). Posteriormente, foram elaboradas a parte designada como aceitadora (A) adicionando o grupo aceitador (terc-butil benzoato) e a parte doadora (D) (trifenilamina) através de acoplamentos catalisados por paládio. Todas as aproximações à introdução da unidade iónicas na cadeia alquilada após desproteção do álcool (R17) verificaram-se infrutíferas.
Na segunda aproximação, optou-se pela inserção de grupos carregados na parte doadora (derivados de trifenilamina), adicionando posteriormente estas unidades integrando as estruturas iónicas (2,3-dimetilimidazólios ou sulfonato) à estrutura do DPP. Foram ensaiadas várias reações de arilação direta ou Suzuki-Miyaura, não se tendo obtido sucesso.
Currently, dye-sensitized solar cells (DSSC) have been the subject of intense research in several research groups due to the advantages that this model offers compared to traditional solar cells. Among these advantages are lower cost, greater flexibility and sustainability. One of the most studied fields in this area is the creation of new organic dyes to act as sensitizers, due to the diversity of structures that can be designed and developed. The diketopyrrolopyrrole (DPP) skeleton, in particular, has demonstrated a lot of potential, thanks to the ease of introducing substituents, particularly on the aromatic rings and amide groups. Another notable factor is the recent use of ionic liquids based on 2,3-dimethylimidazoles as an additive in electrolytes, increasing the energy conversion yield. This fact led to the idealization and synthesis of new diketopyrrolopyrroles, with a D-π-A structure (Donor- π-Acceptor), integrated with positively and negatively charged groups (2,3 dimethylimidizolium and sulfonate). For the introduction of ionic units, two approaches were outlined: i) the introduction of these units into the alkyl chain present in the nitrogen of the DPP lactam ring and, ii) the introduction of the same units into the donor part of the structure. The DPP nucleus substituted by 4-bromophenyl and 2-furanyl groups was first synthesized, and this structure was used as a conjugate bridge (π) in the dyes subsequently synthesized. In the first case, in order to proceed with the introduction of the ionic unit, it was necessary to N-alkylate the nitrogen atom with (2-iodoethoxy)triisopropylsilane (R10). Subsequently, the part designated as acceptor (A) was prepared by adding the acceptor group (tert-butyl benzoate) and the donor part (D) (triphenylamine) through palladium-catalysed couplings. All approaches to introducing the ionic unit into the alkylated chain after deprotection of the alcohol (R17) were unsuccessful. In the second approach, we opted for the insertion of charged groups in the donor part (triphenylamine derivatives), subsequently adding these units integrating ionic structures (2,3-dimethylimidazolium or sulfonate) to the DPP structure. Several direct arylation or Suzuki-Miyaura reactions were tested but were not successful.
Currently, dye-sensitized solar cells (DSSC) have been the subject of intense research in several research groups due to the advantages that this model offers compared to traditional solar cells. Among these advantages are lower cost, greater flexibility and sustainability. One of the most studied fields in this area is the creation of new organic dyes to act as sensitizers, due to the diversity of structures that can be designed and developed. The diketopyrrolopyrrole (DPP) skeleton, in particular, has demonstrated a lot of potential, thanks to the ease of introducing substituents, particularly on the aromatic rings and amide groups. Another notable factor is the recent use of ionic liquids based on 2,3-dimethylimidazoles as an additive in electrolytes, increasing the energy conversion yield. This fact led to the idealization and synthesis of new diketopyrrolopyrroles, with a D-π-A structure (Donor- π-Acceptor), integrated with positively and negatively charged groups (2,3 dimethylimidizolium and sulfonate). For the introduction of ionic units, two approaches were outlined: i) the introduction of these units into the alkyl chain present in the nitrogen of the DPP lactam ring and, ii) the introduction of the same units into the donor part of the structure. The DPP nucleus substituted by 4-bromophenyl and 2-furanyl groups was first synthesized, and this structure was used as a conjugate bridge (π) in the dyes subsequently synthesized. In the first case, in order to proceed with the introduction of the ionic unit, it was necessary to N-alkylate the nitrogen atom with (2-iodoethoxy)triisopropylsilane (R10). Subsequently, the part designated as acceptor (A) was prepared by adding the acceptor group (tert-butyl benzoate) and the donor part (D) (triphenylamine) through palladium-catalysed couplings. All approaches to introducing the ionic unit into the alkylated chain after deprotection of the alcohol (R17) were unsuccessful. In the second approach, we opted for the insertion of charged groups in the donor part (triphenylamine derivatives), subsequently adding these units integrating ionic structures (2,3-dimethylimidazolium or sulfonate) to the DPP structure. Several direct arylation or Suzuki-Miyaura reactions were tested but were not successful.
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Palavras-chave
Dicetopirrolopirrole DSSC Corantes 2,3-dimetilimidazólio Sulfonato Células solares