A compound comprising one or more moieties of formulae -: wherein: R 1, R 2, R 3 and R 4 are each independently selected from hydrogen, fluoro, chloro, bromo, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted amino, substituted or unsubstituted alkoxy, substituted or unsubstituted arylalkoxy, and hydroxyl; each π a independently represents a π-conjugated π-donor ring system formed from one, two, three or four 6-membered aryl or 5 to 6-membered heteroaryl rings; when taken in combination, each π b and π c independently forms a moiety π bc selected from wherein: moieties π bc1 and π bc4 are directly bonded to 1 or 2 boron atoms via either or both nitrogen atoms respectively; moieties π bc1 and π bc4 are directly bonded to 1 or 2 π a moieties via either or both C*; and any or all of the rings forming π a and π bc may be independently optionally substituted with one more ring substituents selected from halo, alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, heterocyclyl, carboxyl, phosphoryl, sulfonyl, hydroxyl, alkoxy, nitro, amino, mercapto, silyl, siloxy, azido, boronic acid group, sulfonic acid group, hydroxamic acid group, cyanoacrylate group, and dioxocyclobutenyl group having at least one functional group selected from the group consisting of a carboxyl, phosphoryl, sulfonyl, hydroxyl, alkoxy, nitro, amino, mercapto, silyl, siloxy, azido, boronic acid group, sulfonic acid group, hydroxamic acid group and cyanoacrylate group. R 1, R 2, R 3 and R 4 are each independently selected from hydrogen, fluoro, chloro, bromo, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted amino, substituted or unsubstituted alkoxy, substituted or unsubstituted arylalkoxy, and hydroxyl; each π a independently represents a π-conjugated π-donor ring system formed from one, two, three or four 6-membered aryl or 5 to 6-membered heteroaryl rings; when taken in combination, each π b and π c independently forms a moiety π bc selected from wherein: moieties π bc1 and π bc4 are directly bonded to 1 or 2 boron atoms via either or both nitrogen atoms respectively; moieties π bc1 and π bc4 are directly bonded to 1 or 2 π a moieties via either or both C*; and any or all of the rings forming π a and π bc may be independently optionally substituted with one more ring substituents selected from halo, alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, heterocyclyl, carboxyl, phosphoryl, sulfonyl, hydroxyl, alkoxy, nitro, amino, mercapto, silyl, siloxy, azido, boronic acid group, sulfonic acid group, hydroxamic acid group, cyanoacrylate group, and dioxocyclobutenyl group having at least one functional group selected from the group consisting of a carboxyl, phosphoryl, sulfonyl, hydroxyl, alkoxy, nitro, amino, mercapto, silyl, siloxy, azido, boronic acid group, sulfonic acid group, hydroxamic acid group and cyanoacrylate group. moieties π bc1 and π bc4 are directly bonded to 1 or 2 boron atoms via either or both nitrogen atoms respectively; moieties π bc1 and π bc4 are directly bonded to 1 or 2 π a moieties via either or both C*; and any or all of the rings forming π a and π bc may be independently optionally substituted with one more ring substituents selected from halo, alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, heterocyclyl, carboxyl, phosphoryl, sulfonyl, hydroxyl, alkoxy, nitro, amino, mercapto, silyl, siloxy, azido, boronic acid group, sulfonic acid group, hydroxamic acid group, cyanoacrylate group, and dioxocyclobutenyl group having at least one functional group selected from the group consisting of a carboxyl, phosphoryl, sulfonyl, hydroxyl, alkoxy, nitro, amino, mercapto, silyl, siloxy, azido, boronic acid group, sulfonic acid group, hydroxamic acid group and cyanoacrylate group.