Excitonically Coupled States in Crystalline Coordination Networks
Haldar, R. / Mazel, A. / Joseph, R. / Adams, M. / Howard, I. A. / Richards, B. S. / Tsotsalas, M. / Redel, E. / Diring, S. / Odobel, F. / Wöll, C. (2017)
Chemistry -A European Journal, 2017, 23, 57, 14316-14322, DOI: 10.1002/chem.201702968
- Date: September 2017
When chromophores are brought into close proximity, noncovalent interactions (π–π/CH–π) can lead to the formation of excitonically coupled states, which bestow new photophysical properties upon the aggregates. Because the properties of the new states not only depend on the strength of intermolecular interactions, but also on the relative orientation, supramolecular assemblies, where these parameters can be varied in a deliberate fashion, provide novel possibilities for the control of photophysical properties.
This work reports that core-substituted naphthalene diimides (cNDIs) can be incorporated into surface-mounted metal– organic structures/frameworks (SURMOFs) to yield optical properties strikingly different from conventional aggregates of such molecules, for example, formed in solution or by crystallization. Organic linkers are used, based on cNDIs, well-known organic chromophores with numerous applications in different optoelectronic devices, to fabricate MOF thin films on transparent substrates. A thorough characterization of the properties of these highly ordered chromophoric assemblies reveals the presence of non-emissive excited states in the crystalline material. Structural modulations provide further insights into the nature of the coupling that gives rise to an excited-state energy level in the periodic structure.