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By fluorescence spectroscopy it has been established that coal derived asphaltene (CDA) forms aggregates in CCl4medium. The new feature of this compound is that even before aggregate formation it can incorporate water molecules and the critical aggregation concentration (CAC) in nonaqueous medium increases with increase in ω (= water:CDA mole ratio). The fluorescence spectroscopic determination of the equilibrium constant (K) of the molecular complex of [60] fullerenes with CDA in carbon tetrachloride medium has revealed thatKincreases on addition of microquantities of water. This observation has been rationalized by assuming that the nitrogenatoms at one end of CDA molecules attach themselves to the water micropool and thus producing a different conformation with a wider distance at the other end. This pre-organization further facilitates inclusion. By utilizing fluorescence variation of [60]fullerene/CDA complex in CCl4as continuous medium with change in ω a critical ω (=5) has been found. The formation of CDA/[60]fullerene complex has also been established by NMR spectroscopy. [ABSTRACT FROM PUBLISHER]

Coal-derived asphaltene (CDA) has been shown to form electron donor–acceptor-type molecular complexes with electron acceptor such as 2,5-cyclohexadiene-1,4-diylidene also known as tetracyanoquinodimethane (TCNQ) in homogeneous medium of carbon tetrachloride and heterogeneous medium of aqueous SDS. This has been investigated both by UV-Vis and fluorescence spectrophotometric method. The Charge transfer (CT) absorption peaks have been detected by difference spectral method and the wavelengths of the CT peaks are close in both the medium. The formation constants (K) have been determined using the Benesi–Hildebrand equation. The magnitudes ofKare in the order of 103 L mol−1that are comparable to some supramolecular or inclusion complexes. The study reveals the presence of π-donor (i.e., aromatic) type of compounds in CDA molecule. It also supports the view that CDA molecules exist in solution forming micellar aggregate, in the cavities of which the TCNQ molecules are included. The remarkable increase (three fold) in the formation constant in the SDS medium compared to CCl4further indicates that the CDA aggregate in SDS undergoes some preorganization to further facilitate inclusion. [ABSTRACT FROM PUBLISHER]