Psoralen compounds are synthesized which have substitutions on the 4, 4', 5', and 8 positions of the psoralen, which permit enhanced binding to nucleic acid of pathogens. Higher psoralen binding levels and lower mutagenicity are described, resulting in safer, more efficient, and reliable inactivation of pathogens in blood products. The invention contemplates inactivation methods using the new psoralens which do not compromise the function of blood products for transfusion. In particular, use of 5'-primary aminoalkyl psoralens to inactivate pathogens in platelets is disclosed.