2D correlation spectra edited by the sign of relative coupling constant

Modifications (CSEc and CSEh) of recently published SQSQc and SQSQh pulse sequences are proposed and tested on detection of small (～2 Hz) signed silicon-carbon coupling constants. The new sequences increase signal intensity by simplifying the spectra. The signals are about four times stronger than in SQSQc or SQSQh spectra, achieving the sensitivity of E.COSY-type experiment. The information about sign and magnitude of the coupling is preserved. CSEc and CSEh spectra for two silicon compounds are presented and compared. The two new sequences allow editing of heteronuclear correlation spectra according to the sign of the selected heteronuclear coupling constants.