Conjugated porphyrin dyads have valuable electron-optical properties that make them useful for a variety of applications. Two dyads of palladium(II) β-octaethylporphyrin linked with butenyne bridge to nickel(II) meso-diphenylporphyrin and methyl pyropheophorbide-a, were synthesized using the Sonogashira cross-coupling reaction. Both the dyads exhibited optical properties considerably different from the corresponding components, indicating strong electronic interaction between the units in the dyads both in the ground and excited states, providing fast energy flow between chromophores. The DFT calculations revealed the structural features of the dyads in interconnection with their electronic properties. The conjugation energy gain forced the decrease of the dihedral angle between porphyrin plane and linking carbon-carbon double bond, though at expense of distortion of the diphenylporphyrin ring. The electron transitions upon excitation comprise molecular orbitals centered on both chromophores and their interaction led to emerging new bathochromically shifted Soret band component at 460 nm. The palladium porphyrinate-chlorin dyad exhibits luminescent properties in the red visible range at room temperature, as well as phosphorescence at near-infrared (NIR) at 77 K. In contrast, the palladium-nickel porphyrinate dyad does not emit light, but it absorbs light more effeciently across the entire visible spectrum. Both the dyads feature broad and strong absorption representing panchromatic like dyes. These dyads could be useful as potential photosensitizers for solar light conversion devices.

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