A novel series of extrinsic probes for intracellular pH (pH(i)) determination by H-1 NMR is described. Imidazol-1-ylacetate, malonate, 3-glutarate and 2-succinate esters were synthesized by reaction of imidazole either with alpha-bromoesters or with alpha,beta-unsaturated esters. The corresponding acids were prepared by hydrolysis.