Enumerating Intramolecular Charge Transfer in Conjugated Organic Compounds

Charge transfer across conjugated organic molecules is the functional basis of many optoelectronic and semiconductor devices. The ability to design such molecules to suit a given device application is highly desirable; yet, realizing this prospect is impeded by the lack of an algorithm that quantifies the extent of intramolecular charge transfer (ICT) in absolute terms. In turn, an algorithm to describe ICT is held back by a poor definition of one of its key dependent terms: conjugation. Current equations assume that π-bonding operates solely across two bonds, even though conjugation extends beyond these limits, and such equations only yield relative measures of π-conjugation. This work presents a four-step algorithm that enumerates ICT on an absolute scale. The method is applied successfully to four types of optoelectronic materials; results demonstrate the need to reconsider certain fundamental chemical-bonding and ICT concepts for conjugated molecules. These findings have implications for all optoelectronic and semiconducting materials.