A new class of carbon monoxide-releasing molecules (CO-RMs) are reported based on a previously known tetracarbonyl phenylpyridine manganese(I) motif. A pre-functionalized CO-RM undergoes a direct Pd-catalysed Suzuki–Miyaura cross-coupling with phenylboronic acid to give a π-extended three-ring CO-RM. Cross-coupling conditions were modified to allow coupling of a morpholine-containing boronic acid on to a CO-RM, introducing drug-like functionality. An LED system was used to facilitate controlled CO-release. Irradiation using an LED (400 nm or 365 nm) gives rise to faster CO-release, with lower overall input power than traditional use of a TLC lamp (365 nm), as measured by an assay based on the conversion of deoxymyoglobin to carbonmonoxymyoglobin.