Upon irradiation with the appropriate wavelengths of light, Rubiq and Rubpy undergo ligand exchange with a solvent molecule (in this case, water) due to population of a metal-centered antibonding orbital (Fig. , Supplementary Fig. ). Rubiq and Rubpy exhibit low-energy absorbance bands due to low-lying metal-to-ligand charge transfer (MLCT) states common in ruthenium polypyridyl complexes . As expected, the extended pi bond structure of 2,2'biquinoline gave a bathochromic shift in peak absorbance of Rubiq to a lmax of 535 nm, significantly red-shifted when compared with the 2,2'-bipyridine-containing Rubpy compound and oNB . All crosslinkers exhibited a significant lmax with a slow decay in absorptivity, permitting off-peak photon absorbance and population of antibonding orbitals at low energies (Fig. .). For this study, Rubiq was photocleaved using 617 nm (e = 43 M -1 cm -1 ), Rubpy with 530 nm (e = 14 M -1 cm -1 ), and oNB at 405 nm (e = 118 M -1 cm -1 ), wavelengths commonly accessible through inexpensive LED light sources that balanced photocleavage efficiency and spectral separation. This series of crosslinkers was shown to be unidirectionally orthogonal: red light (617 nm) irradiation led to photolysis of Rubiq only, green light (530 nm) irradiation photolyzed both Rubiq and Rubpy but left oNB intact, and blue light (405 nm) photolyzed all three crosslinkers (Fig. ). This is demonstrated by the presence or absence of a shift in absorbance spectrum upon irradiation; all three compounds undergo a change in their electronic structure upon photolysis which is reflected in the absorbance spectra. The insensitivity of Rubpy to high doses of red light, as well as oNB to extended exposure to red and green light, demonstrates wavelength selectivity of the small molecule crosslinkers in situ.