Pyridyl CO Fixation Enabled by a Secondary Hydrogen Bonding Coordination Sphere

Reversible CO 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 receptors with π-systems is put forward. A series of receptors (five pyridine-based and one triazine-based) are evaluated as CO binders in terms of number of hydrogen bonding sites, strength of hydrogen bond donors, and number of nucleophilic sites. The binding of CO to the receptors was probed by computational models, absorption spectroscopy, fluorescence spectroscopy, cyclic voltammetry, and H NMR studies. Multiple solvents with varying ionic strength additives are probed to analyze the effects on CO-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 binding with each of the analytical techniques. The diaminopyridine motif demonstrates reversible CO binding and has convenient substitution sites for derivatization to incorporate into functional sensor systems.