H₂O-involved hydrogen bonds in pseudo-double-decker supramolecular structure of 1,8,15,22-tetrasubstituted phthalocyaninato zinc complex

A novel dimeric supramolecular structure, {Zn[Pc(α-OC ₅H₁₁)₄]·H₂O}₂, formed from two molecules of 1,8,15,22-tetrakis(3-pentyloxy)phthalocyaninato zinc complex was revealed by X-ray single crystal analysis. With the help of the oxygen atom from the alkoxy substituent attached at the nonperipheral position of the phthalocyanine ring, each H₂O forms two hydrogen bonds, connecting two phthalocyanine molecules to form a pseudo-double-decker supramolecular structure in the crystals with a ring-to-ring separation of 3.728 Å. This, to the best of our knowledge, represents the first example of supramolecular structure formed from phthalocyanine complexes with transition metals via H₂O-involved hydrogen bonding interaction. To enhance understanding of the existence of hydrogen bonds in the solid-state crystal structure of this compound, theoretical calculations on the stabilization energy in a system composed of two Zn[Pc(α-OC₅H₁₁) ₄] moieties as well as in the supramolecular structure {Zn[Pc(α-OC₅H₁₁)₄]·H ₂O}₂ have been performed using the density functional theoretical method. Comparison of the calculated stabilization energy between these two systems together with the natural bond orbital analysis over the later supramolecular structure reveals the dominant H₂O-involved hydrogen bonding interaction over the π~π interaction in {Zn[Pc(α-OC ₅H₁₁)₄]·H₂O}₂.