Self-assembly of rhenium(l)-based molecular rectangles containing long alkyl chains has been achieved in one-pot synthesis by solvothermal methods. An enormous enhancement in the emission intensity, quantum yield, and lifetime of the rectangles has been observed when the solvent medium is changed from organic to aqueous. Addition of water favors the aggregation of Re(l) molecular rectangle resulting in the luminescence enhancement, and this phenomenon has been traced out using light scattering techniques.