Pyridyl CO₂ Fixation Enabled by a Secondary Hydrogen Bonding Coordination Sphere

Abstract

Reversible CO 2 binders under ambient conditions are of significant interest for multiple applications in sensing and capture technologies. In this paper, a general systematic way to evaluate CO 2 receptors with π-systems is put forward. A series of receptors (five pyridine-based and one triazine-based) are evaluated as CO 2 binders in terms of number of hydrogen bonding sites, strength of hydrogen bond donors, and number of nucleophilic sites. The binding of CO 2 to the receptors was probed by computational models, absorption spectroscopy, fluorescence spectroscopy, cyclic voltammetry, and 1 H NMR studies. Multiple solvents with varying ionic strength additives are probed to analyze the effects on CO 2 -bound intermediates. The receptors were screened progressively down-selecting through the different analytical techniques arriving at a promising pyridine receptor, which shows evidence of CO 2 binding with each of the analytical techniques. The diaminopyridine motif demonstrates reversible CO 2 binding and has convenient substitution sites for derivatization to incorporate into functional sensor systems.

Calix[4]pyrrolato gallate: square planar-coordinated gallium(iii) and its metal–ligand cooperative reactivity with CO2 and alcohols

“…† Element-ligand cooperative (ELC) binding of CO 2 is a widely studied reaction with various transition metals [44][45][46][47][48][49][50] and p-block elements [51][52][53][54][55][56][57][58][59] and was also investigated in small molecule contexts other than ELC. 35,[60][61][62][63][64][65][66] To the best of our knowledge, the described reaction represents the rst example for reversible CO 2 xation by a gallium(III) platform. This is achieved by the balanced energetics in dearomatization/rearomatization of one of the pyrrole rings of the calix [4]pyrrolato ligand.…”

Low-Valent Cobalt(I) CNC Pincer Complexes as Catalysts for Light-Driven Carbon Dioxide Reduction

“…Reducing the amount of PPh 3 from 1 equivalent to 0.2 equivalents or using 1 equivalent of DPPP gave a TOF of ∼4 h –1 at 1 h; however, when earlier times were evaluated a TOF of 10.7 h –1 is observed at 0.5 h for the added PPh 3 experiment (Figures S47 and S48). Phosphines are believed to reversibly bind to CO 2 in a manner similar to carbenes and electron-rich imine-type nitrogens. − This reversible binding could serve to bend the CO 2 molecule into a more reactive geometry than the linear form which would allow PPh 3 to serve the role of a catalytic CO 2 activator operating at a rate faster than the Co­(I) catalyst in the PCO 2 RR …”

Electrocatalytic Reduction of CO2 and H2O with Zn(II) Complexes Through Metal‐Ligand Cooperation

“…[24,28] Ligand reduction increases the basicity of the ligand and in conjunction with coordination by the zinc ion facilitates the binding of CO 2 and formation of pyridyl-N coordinated CO 2 intermediate (A). , [55,56] The bound and activated CO 2 could undergo a protonation coupled with reduction, which would lead to a metallacarboxylic acid (B). Metallacarboxylic acids are commonly invoked intermediates in the reduction of CO 2 to yield CO.…”