“…Tpy-metal ion complexes exhibit unique electronic, [3][4][5] chemical, [6][7][8] optical, 3,8,9 photovoltaic, 10 and catalytic 6 properties and have been extensively used in medicinal chemistry, 11 materials science 12 and as catalysts. 6 Specifically, tpy-metal complexes are a vivid field of study with wide range of applications such as i) DNA intercalators, 13,14 ii) catalysts in artificial photosynthesis, 5 in Pulsed electron-electron double resonance spectroscopy PELDOR (pulsed electron-electron double resonance or synonymously double electron-electron resonance, DEER) is a pulse EPR technique commonly performed at cryogenic temperatures that allows measurement of distances between unpaired electrons with angstrom resolution. 26,27 In a nutshell, during a PELDOR experiment a set of unpaired electrons (from here on A spins) is observed using microwave pulses at a frequency ωA, while a second set of unpaired electrons (from here on B spins) is selectively inverted by a microwave pulse at a different frequency, ωB (Fig.…”