2-Hydroxyisoquinoline-1,3(2H,4H)-dione was recently discovered as a scaffold for the inhibition of HIV-1 integrase and the RNase H function of HIV-1 reverse transcriptase. It was investigated its interaction with Mg2+ and Mn2+ using different spectroscopic techniques and report that 2-hydroxyisoquinoline-1,3(2H,4H)-dione forms a 1:1 complex with Mg2+ but a 1:2 complex with Mn2+. Antiviral agent.