Multiphoton excitation and energy transfer pathways in Mn²⁺-sulfonyl calixarene complexes

The complexes based on Mn²⁺ ions and sulfonylcalixarene macrocycles can exhibit, when excited by blue light (360 to 400 nm), a broad luminescence band around 600 nm, resulting from the d-d transition ⁴T₁(t₂g⁴eg¹) → ⁶A₁(t₂g³eg²) of the Mn²⁺ ions. A new original synthetic route to access the phenylethynylsulfonylcalix[4]arene macrocycle (paThiaSO₂) and its corresponding complexes with Mn²⁺ ions has been followed and the first experience via excitation with lower-energy multiphoton absorption have been realized. The results obtained demonstrate the possible two-photon sensitization of Mn²⁺ ions through the sulfonylcalixarene macrocycle.