Two novel potent perfluorophenylhydrazone derivatives, 1-((4-bromothiophen-2-yl)methylene)-2-(perfluorophenyl) hydrazine, and 1-((4-bromo-5-methylthiophen-2-yl)methylene)-2-(perfluorophenyl)hydrazine as multi-target compounds to combat Alzheimer disease and their crystal, molecular, and electronic properties