Tuning of Optoelectronic Properties in Oligo(phenyleneethynylene)-Based Cocrystals through Modulation of Charge-Transfer Interactions

Organic multicomponent cocrystals with semiconducting
properties
have gained wide interest due to their potential in solid-state optoelectronic
applications. Herein, we report the design and synthesis of an oligo(phenyleneethynylene)
(OPE) derivative and its cocrystals with 2,3,5,6-tetrachloroterephthalonitrile
(TCPN) and 1,2,4,5-tetracyanobenzene (TCNB) to explore the optical
properties and charge-transfer interactions. The optical property
of the charge-transfer cocrystals was dependent on the in-crystal
geometry of luminophore OPE and charge-transfer interactions. The
study also explored the role of molecular packing and intermolecular
interactions on photoluminescence properties in the crystalline state
of OPE, OPE–TCPN, and OPE–TCNB using structural data
obtained from single-crystal X-ray diffraction. The theoretical investigation
of the molecular assemblies demonstrated that the mixed-stacked systems
allow a broader range of tunability in electronic properties compared
to single-component systems. Combining different molecules (TCPN and
TCNB) of complementary electronic structures of OPE, we could modulate
parameters such as the band gap, charge carrier mobility, and energy
levels more precisely.