Iron doping in sodium para-nitrophenolate dihydrate crystal: A case study

Abstract

In this study we examine a case of iron doping in sodium para-nitrophenolate dihydrate single crystal recently reported by Dalal and Kumar (Mater. Lett. 165 (2016) 99-102). We show that, addition of ferric (Fe3+) ions into an aqueous solution of sodium 4-nitrophenolate dihydrate (1) results in immediate precipitation of an insoluble brown hydrous iron(III) oxide, which precludes any doping (incorporation) of iron in (1). The crystals grown after filtering the precipitate show a negative spot test for iron and exhibit sharp proton resonances in the 1H NMR spectrum proving no incorporation of iron in (1). In addition to highlighting the importance of the reactive chemistry of the dopant and the host for crystal growth from solution, we show that ferric ions cannot be doped into a host material whose aqueous solution is alkaline.