Modulation of the CO₂ fixation in dinickel azacryptands

Abstract

While bimetallic azacryptands are known to selectively coordinate CO, there is little knowledge on how different substitution patterns of the azacryptand cage structure influence CO coordination. Stopped-flow UV-vis spectroscopy, electrochemical analysis and DFT calculations were performed on a series of dinickel azacryptands and showed different rates of CO coordination to the complexes. We herein present data showing that the different flexibility of the azacryptands is directly responsible for the difference in the CO uptake capability of dinickel azacryptand complexes.

CoIICryptates Convert CO2into CO and CH4under Visible Light

“…The protono ft he -CCH group ap-Scheme1.Octaazacryptates that can fix atmospheric CO 2 . [26][27][28] Figure 1. Octaazacryptate used for homogeneousCO 2 photoreduction.…”

“…The coordination environment of Cu II with coordination number 5 was also observed in Zn II and Co II cryptates, whereas an octahedral geometry was found around Ni II in its cryptate complexes (Scheme ). In fact, Apfel et al . performed a deep investigation of Ni II cryptates with different spacers and their ability to selectively fix CO 2 (Scheme ).…”

“…The coordination environmento fC u II with coordination number 5w as also observed in Zn II and Co II cryptates, whereas an octahedral geometry was found aroundN i II in its cryptatec omplexes (Scheme 1). In fact, Apfel et al [27,28] performed ad eep investigation of Ni II cryptates with different spacers and their ability to selectively fix CO 2 (Scheme 1). This extensive study showed that the coordination of CO 2 can be modulated by cage linkers (Scheme 1), almostd isappearing, or becoming very slow,w hen the cryptandsf unctional groups point towards the cryptandc avity.O nt he other hand, when functional groups are oriented in the opposite way,C O 2 fixation increased in inverse proportionality to the substituent bulkiness (tBu !…”

“…As a follow up of the work previously reported on octaazacryptands and the lack of detailed studies on the role of substituents on the photoreduction of CO 2 by Co II cryptates, our work complements those studies. As it is clear that the substituents on the octaazacryptates influence the capture of CO 2 into bicarbonate, our main goal was to understand how they affect the CO 2 conversion, and, more specifically, photoreduction. The aim is to contribute to the understanding of the patterns of the selectivity of the CO 2 photoreduction products—one of the main challenges in CO 2 conversion.…”

Captura e Conversão de Dióxido de Carbono: a Promoção de um Resíduo a Produto de Valor Acrescentado

“…Esta semelhança demonstra o potencial deste tipo de compostos para mimetizar processos já encontrados na natureza! Mais tarde Moller e a sua equipa [10,11] desvendaram que alterações nas estruturas destes criptatos (Figura 5) tinham influências dramáticas na seletividade para determinados aniões. Neste projeto pretendeu-se entender esta influência tanto na captura de CO 2 como na sua conversão em produtos de valor acrescentado.…”