Refractometric parameters of nonlinear optical molecular cocrystals based on the aminopyridine series

Refractive indices of new nonlinear optical materials based on 4-nitrophenol cocrystals with the aminopyridines 2-aminopyridine, 2,6-aminopyridine, and 4-aminopyridine have been studied. The refractive indices of the compounds under study are presented: $n$ = 1.694 (optical microscopy) and 1.605 (Abbe method) for 2-aminopyridine-4-nitrophenol (2AP4N), $n$ = 1.541 (optical microscopy) and 1.589 (Abbe method) for 2,6-diaminopyridine-4-nitrophenol (2,6DAP4N), and $n$ = 1.561 (optical microscopy) and 1.591 (Abbe method) for 4-aminopyridine-4-nitrophenol (4AP4N).