LAUSR

Abstract This essay is dedicated to Helmut Schwarz on his 75th Birthday. It is written based on my diary notes, and covers the period from the early 1980s to the present time. It describes two periods of our scientific collaboration, on: (a) Two-state reactivity (TSR), which has become a widely used concept in bioinorganic and metallo-enzymatic chemistry; and (b) the mechanistic variants of methane activation, which is still ongoing. In between, the essay tells the story of the Lise Meitner-Minerva Center for Computational Quantum Chemistry, in which Helmut played a major role during the establishment of the Center and as the Chairman of its Advisory Board for 20 years. A few words are devoted to the role of Helmut as a statesman and for his making the Alexander von Humboldt Foundation a vehicle for worldwide scientific influence. This essay is basically a story of science and friendship.