TLD1433 is the first Ru(II) complex to be tested as a photodynamic therapy agent in a clinical trial. In this contribution we study TLD1433 in the context of structurally‐related Ru(II)‐imidozo[4,5‐f][1,10]phenanthroline (ip) complexes appended with thiophene rings to decipher the unique photophysical properties which are associated with increasing oligothiophene chain length. Substitution of the ip ligand with ter‐ or quaterthiophene changes the nature of the long‐lived triplet state from metal‐to‐ligand charge‐transfer to 3ππ* character. The addition of the third thiophene thus presents a critical juncture which not only determines the photophysics of the complex but most importantly its capacity for 1O2 generation and hence the potential of the complex to be used as a photocytotoxic agent.

The excited state properties of three heteroleptic copper(I) xantphos 4H-imidazolate complexes are investigated by means of femtosecond and nanosecond time-resolved transient absorption spectroscopy in dichloromethane solution. The subpicosecond spectral changes observed after excitation into the MLCT absorption band are interpreted as intersystem crossing from the singlet to the triplet manifold. This interpretation is corroborated by DFT and TD-DFT results, indicating a comparable molecular geometry in the ground state (and hence the nonrelaxed singlet state) and the excited triplet state. Population of the triplet state is followed by planarization of the N-aryl rings of the 4H-imidazolate ligand on a 10 ps time scale. The planarization strongly depends on the substitution pattern of the N-aryls and correlates with the reduced moment of inertia for the planarization motion. The triplet state subsequently decays to the ground state in about 100 ns. These results demonstrate that the excited state processes of copper(I) complexes depend on the specific ligand(s) and their substitution pattern. Thus, the work presented points to a possibility to design copper(I) complexes with specific photophysical properties.

The class of cyclic lipopeptide natural products consists of compounds with a diverse range of bioactivities. In this study, we elucidated the structure of the cyclic lipopeptide anikasin using X-ray crystallography, analyzed its biosynthetic gene cluster, and investigated its natural role in the interaction between the producer strain Pseudomonas fluorescens HKI0770 and protozoal predators. These results led to the conclusion that anikasin has dual functionality enabling swarming motility and acting as a niche amoebicide, which effectively inhibits the social amoeba Polysphondylium violaceum and protects the producer strain from protozoal grazing.