Prediction and Rationalization of Different Photochemical Behaviors of mer- and fac-Isomers of [Ru(pyridyltriazole)3]2+

Facial and meridional isomerism of metal complexes is known to result in fundamental differences in photophysical properties. One may also envisage differences in their photochemical reactivity and therefore predict different outcomes of their light-triggered transformations. The fac- and mer-isomers of the complex [Ru(pytz)3]2+ (fac-1 & mer-1, pytz = 1-benzyl-4-(pyrid-2-yl)-1,2,3-triazole) were separated and isolated. mer-1 undergoes a predicted pytz photodechelation process in acetonitrile to yield trans-[Ru(κ2-pytz)2(κ1-pytz)(NCMe)]2+ (2) whereas unfavorable interligand steric interactions are predicted to, and indeed do prevent comparable photoreactivity for fac-1. Reversible photoisomerization of fac-1 and mer-1 is also observed, however. The differences in photochemical reactivity of the two isomers can be rationalized based on structural programming of the preferential accessibility of particular 3MC excited states due to differences in their interligand steric interactions. Here we present an initial predictive thought experiment, subsequent experimental verification, and computational rationalization of the differences in photochemical reactivity of these two isomeric complexes.


Figure S9
Spectral output profile of 23 W CFL irradiation source S9

Figure S10
Electrospray mass spectrometry data recorded during the photolysis of 1 S10

Figure S12
Spectral output profile of blue LED irradiation source S10

Figure S13
SONO plots for the 3 MCtrans states of fac-1 and mer-1 S11

Figure S14
SONO plots for the 3 MCcis states of mer-1 S11

Figure S15
SONO plots for the 3 MCpenta states of fac-1 and mer-1 S12

Figure S17
Selected calculated molecular orbital plots for 2 S13

Figure S19
SONO plots for the 3 MLCT state 2 S14

Figure S22
Selected calculated molecular orbital plots for 3 S15

Figure S18 .
Figure S18.Calculated UV-visible absorption spectrum for 2 from TDDFT.The blue trace used 0.15 eV full-width at half-maximum line broadening.

Table S1 .
Selected TDDFT transitions for fac-1 and mer-1 and their dominant composition and character.