Mixed CO/NO-releasing molecules were prepared by conjugation of the 17-electron rhenium dicarbonyl cis-[Re(CO)₂Br₄]²⁻ complex to N-nitrosamine modified cyanocobalamin (B12) bio-vectors. The species were fully characterized by standard analytical techniques, including X-ray crystallography for cyanocobalamin-5′-O-pyrazine and (1) and its...