Use of a unique supramolecular assembly of a pyridylphosphine ligand and a metal centered porphyrin complex is shown to give unprecedented selectivities to branched aldehydes via rhodium catalyzed hydroformylation of unsubstituted linear alpha-olefins such as propylene and 1-octene. Increasing the syngas pressure is shown to have a beneficial effect on branched aldehyde selectivity as is increasing the ratio of carbon monoxide to hydrogen used in the hydroformylation reaction.