ADEQUATE CR:13C connectivity mapping in indirect detection mode with composite refocusing

Abstract

We report a novel rare spin correlation experiment termed ADEQUATE with composite refocusing (CR), which is the 1H-detected version of 2D INADEQUATE CR. ADEQUATE CR begins with a polarization transfer from protons to the attached carbon, followed by 13C–13C double-quantum (DQ) preparation. Unlike the ADEQUATE class of experiments, 13C DQ coherence is converted after evolution to single-quantum single transitions (SQ-STs) by CR. 13C SQ-ST is then transferred back to the coupled protons by a coherence order selective reconversion. The present sequence produces partial transition selectivity in the 1H dimension as does 1H Indirect detected 13C Low-Abundance Single-transition correlation Spectroscopy (HICLASS), thereby mitigating the reduction in sensitivity enhancement because of the presence of homonuclear proton couplings. However, unlike HICLASS (which is an experiment that involves SQ-TS evolution), no homonuclear zero quantum mixing is required on the 13C channel in the present experiment. Experimental results are demonstrated on a variety of samples, establishing the efficiency of the proposed method.