Two-and three-armed ligands, like bis(N-acylamidines) 7 and 9, tris(N-acylamidines) 8 and bis(1,3,5-triazapenta-1,3-dienes) 10 with different spacers between the ligand moieties, have been easily prepared in moderate-to-good yields starting from diamines, triamines or dicarboxylic acid derivatives. Thus, the reaction of diamines and triamines with Nacylimidates 3 led to bis(N-acylamidines) 7 and tris(N-acylamidines) 8, respectively, linked through the amino group. Ligands 9, interconnected through the carbonyl groups, were

Keywords: Aggregation / Computational chemistry / Conformation analysis / Scanning probe microscopy / Self-assembly / Tautomerism N-Acylamidines 1a-q, which are important ligands for metal ion complexation, were easily prepared either by acylation of amidines 2 or by treatment of N-acylimidates 3 with amines. Additionally, the reaction of amidinium salts with aroyl halides in the presence of sodium hydroxide gave the aryl derivatives 1r-1ad and three azobenzene derivatives 1ae-1ag.The respective substitution pattern of these novel derivatives was selected with respect to possible steric and electronic effects in coordination reactions as well as with regard to the aggregation properties. N-Acylamidines 1 may exist as three types of tautomers, which were examined in solution by NMR spectroscopic analysis and by quantum chemical DFT and SCS-MP2-calculations for single molecules in the gas phase. Internal rotations require activation energies between

Properties of N-Acylamidines. -A library of N-acylamidines bearing three different aromatic or aliphatic substituents is prepared using various synthetic pathways. Tautomerism and aggregation bahavior is studied in correlation to the substitution pattern. -(WIGBERS, C.; PRIGGE, J.; MU, Z.; FROEHLICH, R.; CHI, L.; WUERTHWEIN*, E.-U.; Eur.