Substituted aryl-fluoroborates as imaging agents

A positron emitting compound or salt thereof, wherein the compound has the formula:

• wherein:
• B is boron;
• A is a single substituted aromatic ring or an aromatic ring joined to one or more additional rings to form a substituted polycyclic moiety, wherein ring atoms comprise carbon and optionally, one or more heteroatoms, and substituents of the aromatic ring or polycyclic moiety other than B comprise at least one electron-withdrawing group (EWG);
• each (Y1)n is independently selected from the group consisting of R1, 18F and 19F, and n=1 or 2;
• Y2 is selected from the group consisting of R1, 18F and 19F;
• R1 is a non-interfering substituent with regard to fluorination of B;
• providing that at least one of (Y1)n and Y2 is 18F;
• providing that σtotal for all substituents on the aromatic ring or polycyclic moiety except B is about 0.06 or more when said at least one EWG is positioned ortho to B, or about 0.2 or more when no EWG is positioned ortho to B;
• and providing that said at least one EWG is not a single bromomethyl group positioned ortho to B.