This dissertation aims to understand the effect of incompatible side chains on the complexes of pi-conjugated electron-rich donors and electron-deficient acceptors in solution. The role of incompatible side chains were studied in simple mixtures of organic donor and acceptor molecules that form donor-acceptor complexes. The incompatible branched and linear alkane side chains on the acceptor and donor respectively prevented complex formation between naphthalene diimide acceptor and naphthalene ether donor. However, the incompatible hydrocarbon-fluorocarbon and polar-non polar side chain pairs did not affect complex formation between the donor and acceptor. In quaterthiophene-naphthalene diimide dyads, the incompatibility of the side chain on the acceptor with respect to the side chain on the donor do not have any influence on the donor-acceptor complex formation. Irrespective of the attached side chains, all the dyads show charge transfer absorption bands and have similar electron transfer rates. The effect of point of attachment of the acceptor to the donor in the quaterthiophene-flavin dyad is also studied.