Amyloid plaque aggregation inhibitors and diagnostic imaging agents

A pharmaceutical composition, comprising a compound of Formula III and a pharmaceutically acceptable excipient or diluent, wherein a compound of Formula III is selected from:

• or a pharmaceutically acceptable salt thereof, wherein
• R3 is hydrogen or -L-Ch;
• R1 and R2 are independently hydrogen, C1-4 alkyl, C2-4 aminoalkyl, C1-4 haloalkyl, haloarylalkyl, -L-Ch, or R1 and R2 are taken together with the nitrogen to which they are attached to form a 5- to 7-member heterocyclic ring optionally having O, S or NR5 in said ring, where
• R5 is hydrogen or C1-4 alkyl;
• L is a covalent bond or linking group selected from the group consisting of:
• —(CH2)n—, or —(CH2)n—C(O)— where
• n is an integer from 0 to 5;
• and
• Ch is a tetradentate ligand capable of complexing with a metal;
• with the proviso that one and only one of R1, R2 and R3 is -L-Ch.