Tryptophan-[Re₆Se₈I₆]³⁻ Cluster Interaction: A Computational Study

The interaction between tryptophan (Trp) and the [Re₆Se₈I₆]³⁻ cluster is studied here using density functional theory calculations including relativistic scalar interactions via the zero-order regular approximation and solvent effects, which we describe in terms of interaction energies, Mulliken charge analysis and molecular orbitals. In the indole functional groups of the Trp-[Re₆Se₈I₆]³⁻ cluster conjugates, modification of the molecular orbitals associated with Trp occurs because states associated with the [Re₆Se₈I₆]³⁻ cluster and the hybrid orbitals have a mixed metal–molecule character, which is attributed to the stronger than expected π interactions facilitated by the indole group in Trp. Here, we find that the energy transfer from hybrid states of Trp-[Re₆Se₈I₆]³⁻ to clusters could reduce intrinsic fluorescence intensity of Trp in the conjugated system.