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 (Fe 3+ ) ions into an aqueous solution of sodium para -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 1 H 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.