A metal-bearing coordination network synthesised from Re(2,2′-bipyridine-5,5′-dicarboxylate)(CO)₃Cl bridging ligands and Cu(II) nodes, [{Cu(DMF)(H₂O)[LRe(CO)₃Cl]}·DMF]_∞ReCu, undergoes an irreversible photoinduced charge transfer process. We demonstrate using time-resolved IR spectroscopy the nature of this photoinduced process and how, under suitable conditions, it is possible to initiate irreversible modification of the crystal through induction of the charge transfer process. As a result we are able to use the photoinduced process, which arises purely as a result of the structure of the coordination network, to write on crystals.