Getting in tune: Systematic tuning of the electronic properties of modular non-heme iron coordination complexes can be used to extract important information on the reaction mechanism and intermediates, which, in turn, help to explain the activity of these systems as water oxidation catalysts ; We would like to thank Prof. J. Mayer, Dr. L. Que, Jr., Dr. W. R. Browne and Dr. X. Ribas for their comments, the European Research Council for FP7-PEOPLE-2010-ERG-268445 and ERC-2009-StG-239910, MICINN for CTQ2012-37420-C02-01 (M. C.), and CTQ2011-23156/BQU (J. M. L.) for the Ramon y Cajal contract (J. Ll.-F) and for PhD grants (I. G.-B. and I. P.), Generalitat de Catalunya for an ICREA Academia Award and Catexel for their generous gift of tritosylTACN