Donoracceptorjärjestelmät

Donor–acceptorjärjestelmät are molecular or supramolecular assemblies in which an electron-rich donor unit interacts with an electron-accepting unit. These systems support charge transfer from donor to acceptor upon photoexcitation or thermal activation, producing transient or, in some cases, persistent charge separation. Donor–acceptor motifs occur as discrete molecular pairs, donor–acceptor copolymers, and interfacial or layered structures used in organic electronics and photochemistry.

Electronic structure and mechanism: The efficiency of charge transfer depends on the relative energies of the donor’s highest occupied molecular orbital (HOMO) and the acceptor’s lowest unoccupied molecular orbital (LUMO), as well as the electronic coupling between the units. An appropriate offset between donor HOMO and acceptor LUMO enables favorable transfer after excitation, while too large offsets increase energy losses. Marcus theory provides a common framework for describing transfer rates and reorganization energies.

Architectures: Donor–acceptor systems can be arranged as discrete molecular pairs, donor–acceptor copolymers, or interfacial layers in devices. Common acceptors include fullerenes and various π-acceptor units; donors are typically electron-rich aromatic motifs. The structural choice controls absorption properties, exciton diffusion, charge separation, and transport across interfaces.

Properties and applications: CT interactions often introduce broad, low-energy absorption bands and solvatochromic shifts. In devices, efficient donor–acceptor separation at interfaces enables organic photovoltaics, light-emitting diodes, and photodetectors. They are also explored in sensors and catalysis.

Terminology: In Finnish literature, the term donoracceptorjärjestelmät is used to describe these concepts, sometimes hyphenated as donor–acceptorjärjestelmät.