C-13 CP (cross-polarization) MAS (magic angle spinning) NMR and GIAO-CHF calculations of buspirone analogues part 1. 3a,4,7,7a-Tetrahydro-2-{4-[4-(2-quinolinyl)-1-piperazinyl]butyl}-4,7-ethane-1H-isoindole-1,3(2H)-dione hydrochloride and hydrobromide

C-13 CP (cross-polarization) MAS (magic angle spinning) solid state NMR spe ctra of buspirone analogue 3a,4,7,7a-tetrahydro-2-{4-[4-(2-quinolinyl)-1-pi perazinyl]butyl}-4,7-ethane-1H-isoindole-1,3(2H)-dione were recorded. In th e spectra of hydrochloride and hydrobromide, two sets of signals appeared, in agreement with single crystal X-ray diffraction data indicating that in each of the salts two independent cations were present in the crystal unit. The largest shielding differences of 3.2-4.6 ppm between two sets of signa ls were found for quinoline aromatic carbons C3 and C2. Ab initio calculati ons of the carbon and nitrogen shielding constants were performed with the use of the GIAO-CHF method for structural fragments: N-butylsuccinimide, qu inoline-(N-methyl) piperazine hydrochloride and hydrobromide. Linear correl ations between theoretical and solid state results were obtained, thus enab ling a reasonable assignment of carbon resonances of the conformations pres ent in the solid state. Due to the fast dynamics in solution, the carbon ch emical shifts corresponded to the averaged values of the forms present in t he solid state. (C) 1998 Elsevier Science B.V. All rights reserved.