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	Direct observation by time-resolved infrared spectroscopy of the bright and the dark excited states of the [Ru(phen)2(dppz)]2+ light-switch compound in solution and when bound to DNA Fergus Poynton , James P. Hall , Paraic Keane , Christine Schwarz , Igor V. Sazanovich , Mike Towrie , Thorfinnur Gunnlaugsson , Christine J Cardin , David Cardin , Susan J. Quinn , Conor Long , John Kelly Chemical Science 7, 3075-3084 DOI: 10.1039/C5SC04514B Open Access Show Abstract ▼ Abstract: The [Ru(phen)2(dppz)]2+ complex (1) is non-emissive in water but is highly luminescent in organic solvents or when bound to DNA, making it a useful probe for DNA binding. To date, a complete mechanistic explanation for this “light-switch” effect is still lacking. With this in mind we have undertaken an ultrafast time resolved infrared (TRIR) study of 1 and directly observe marker bands between 1280–1450 cm−1, which characterise both the emissive “bright” and the non-emissive “dark” excited states of the complex, in CD3CN and D2O respectively. These characteristic spectral features are present in the [Ru(dppz)3]2+ solvent light-switch complex but absent in [Ru(phen)3]2+, which is luminescent in both solvents. DFT calculations show that the vibrational modes responsible for these characteristic bands are predominantly localised on the dppz ligand. Moreover, they reveal that certain vibrational modes of the “dark” excited state couple with vibrational modes of two coordinating water molecules, and through these to the bulk solvent, thus providing a new insight into the mechanism of the light-switch effect. We also demonstrate that the marker bands for the “bright” state are observed for both Λ- and Δ-enantiomers of 1 when bound to DNA and that photo-excitation of the complex induces perturbation of the guanine and cytosine carbonyl bands. This perturbation is shown to be stronger for the Λ-enantiomer, demonstrating the different binding site properties of the two enantiomers and the ability of this technique to determine the identity and nature of the binding site of such intercalators.	Jan 2016
B23-Circular Dichroism	The importance of loop length on the stability of i-motif structures Sarah Gurung , Christine Schwarz , James P. Hall , Christine J. Cardin , John A. Brazier Chemical Communications 51 (26), 5630 - 5632 DOI: 10.1039/C4CC07279K PMID: 25686374 Diamond Proposal Number(s): [9684, 10076] Open Access Show Abstract ▼ Abstract: Using UV and srCD spectroscopy it is found that loop length within the i-motif structure is important for both thermal and pH stability, but in contrast to previous statements, it is the shorter loops that exhibit the highest stability.	Jan 2015

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Direct observation by time-resolved infrared spectroscopy of the bright and the dark excited states of the [Ru(phen)2(dppz)]2+ light-switch compound in solution and when bound to DNA