Molecular structures of chalcone podands: A prognosis of photoinduced transformations in the crystals

A series of chalcone podands with the propenone group in the ortho position of the bridging aryl substituent with respect to the oxyethylene fragment is synthesized. The influence of the preorganization of the chalcone podand molecules in crystals on their ability to participate in topochemical reactions is investigated. From analyzing the X-ray structural data, the highest probability of the solid-state photochemical [2 + 2]cycloaddition is predicted for podands with phenyl substituents and the oxyethylene fragment containing two or three oxygen atoms. The X-ray structural data for the chalcone podand C32H26O4 (3a) are as follows: a = 7.904(9) A, b = 14.92(2) A, c = 21.30(3) A, β = 91.7(1)o, monoclinic system, space group P21/c, Z = 4, V = 2510(5) A3, ρ = 1.26 g/cm3, and R = 0.046; C34H30O5 (3b): a = 15.738(9) A, b = 11.889(2) A, c = 15.0830(15) A, β = 105.47(14)o, monoclinic system, space group C2/c, Z = 4, V = 2720.0(9) A3, ρ = 1.266 g/cm3, and R = 0.0418; C32H24N2O8 (4a): a = 17.9416(18) A, b = 10.9703(8) A, c = 41.699(2) A, β = 105.970(11)o, monoclinic system, space group P21/c, Z = 4, V = 2781.4(5) A3, ρ = 1.348 g/cm3, and R = 0.0426; C36H32N2O10 (4c): a = 7.6286(5)A, b = 17.9398(10) A, c = 11.5890(3)A, β = 95.287(4)o, monoclinic system, space group P21/n, Z = 2, V = 1579.27(14) A3, ρ = 1.372 g/cm3, and R = 0.0377; and C28H22O6 (5a): a = 15.6032(10) A, b = 8.1131(5) A, c = 17.7334(11) A, β = 91.381(5)o, monoclinic system, space group C2/c, Z = 4, V = 2244.2(2) A3, ρ = 1.345 g/cm3, and R = 0.0309.