The antibacterial effect of Mn(II), tetraphenyl porphyrin (TPP),ebselen-porphyrin conjugate 1 and its manganese(II) complex 2 towards Staphylococcus aureus growth was studied by stop-flow microcalorimetry. By analyzing the power-time curves, crucial parameters such as rate constant of bacterial growth (k), half inhibitory concentration (IC50), and generation time (t(G)) were determined. The sequence of the antibacterial activities of these compounds tested was 2 > 1 > Mn(II) > TPP, with an IC50 value of 100 mu g/mL for complex 2. Manganese(II) ebselen-porphyrin conjugate 2 is proposed to benefit from synergetic effects of Mn(II) and 1. (C) 2008 Elsevier B.V. All rights reserved.