Tuning the reactivity in classic low-spin d6 rhenium(I) tricarbonyl radiopharmaceutical synthon by selective bidentate ligand variation (L,L'-Bid; L,L'= N,N', N,O, and O,O' donor atom sets) in fac-[Re(CO)3(L,L'-Bid)(MeOH)]n complexes.

A range of fac-[Re(CO)3(L,L′-Bid)(H2O)]n (L,L′-Bid = neutral or monoanionic bidentate ligands with varied L,L′ donor atoms, N,N′, N,O, or O,O′: 1,10-phenanthroline, 2,2′-bipydine, 2-picolinate, 2-quinolinate, 2,4-dipicolinate, 2,4-diquinolinate, tribromotropolonate, and hydroxyflavonate; n = 0, +1) has been synthesized and the aqua/methanol substitution has been investigated. The complexes were characterized by UV–vis, IR and NMR spectroscopy and X-ray crystallographic studies of the compounds fac-[Re(CO)3(Phen)(H2O)]NO3·0.5Phen, fac-[Re(CO)3(2,4-dQuinH)(H2O)]·H2O, fac-[Re(CO)3(2,4-dQuinH)Py]Py, and fac-[Re(CO)3(Flav)(CH3OH)]·CH3OH are reported. A four order-of-magnitude of activation for the methanol substitution is induced as manifested by the second order rate constants with (N,N′-Bid) < (N,O-Bid) < (O,O′-Bid). Forward and reverse rate and stability constants from slow and stopped-flow UV/vis measurements (k1, M–1 s–1; k–1, s–1; K1, M–1) for bromide anions as entering nucleophile are as follows: fac-[R...