CHEMICAL PRESSURE EFFECT BY SELECTIVE DEUTERIATION IN THE MOLECULAR-BASED CONDUCTOR, 2,5-DIMETHYL-N,N'-DICYANO-P-BENZOQUINONE IMMINE-COPPERSALT, (DME-DCNQI)(2)CU

The mixed-valence copper salt of DMe-DCNQI (1, where DMe-DCNQI = 2,5-d imethyl-N,N'-dicyano-p-benzoquinone diimine) is a molecular conductor whose electrical and magnetic properties are quite sensitive to pressu re. We have performed selective deuteriation of the molecule 1. By con trol of the position and number of deuterium atoms, the low-pressure r egion (less than or similar to 500 bar)dagger in the pressure-temperat ure phase diagram of (1)(2)Cu was reproduced at ambient pressure. The equivalency of the deuteriation and pressure effects is explained from steric origins; 'contraction' aroused by the slightly shorter C-D bon d (steric isotope effect) and 'constriction' by pressure.