Single mode (either T-1 or T-2) contrast agents employed during magnetic resonance imaging owe their advantage over their dual counterparts to the fact that they do not involve any quenching caused by interference between the two modes. The chemistry involving oxides of manganese is highly significant due to their applicability as MRI contrast agents. Manganese oxides are usually known to display a dominant T-1 relaxation enhancement. But, in this work, an engineered structure of manganese oxide (Mn2O3) nanoparticles encapsulated within mesoporous carbon frameworks was developed which exhibited dominant T-2 contrast enhancement, through regulation of contact between the magnetic ion and water. Microstructural characterization revealed that the mesoporous carbon frameworks were spherical in shape and the nanoparticles within them had an average size of 40-50 nm. Relaxivity measurement, MRI experiments and cell viability assay convincingly established the system as a new class of biocompatible T-2 based magnetic resonance imaging agent.