Two-photon absorption spectrum and characterization of the upper electronic states of the dye IR780

Sensitization of Nd3+ Luminescence by Simultaneous Two-Photon Excitation through a Coordinating Polymethinic Antenna

“…As projected, the prominent band around 780 nm is preserved for the first excited state of the polymethine antenna. We notice that this antenna band decreases its absorptivity (as in the case of free ligands), most likely due to small changes in the planarity of the polymethinic chain. , As mentioned previously, it is important that the symmetry of the excited states is preserved since this is directly related to their nonlinear absorption properties. ,,, These bands remain present in both IR-phenNd­(DBM) 3 and IR-tpyNd­(DBM) 3 in the region around 440 nm. In Figure , we include vertical arrows to indicate the wavelength of the femtosecond two-photon excitation pulses for the main experiments (865 nm, see below).…”

“…In Figure , we include vertical arrows to indicate the wavelength of the femtosecond two-photon excitation pulses for the main experiments (865 nm, see below). It should be noted that the maximum two-photon absorbance of the IR-780 chromophore lies at 875 nm; however, this wavelength is not within the reach of our Ti:Sapphire laser system. The two-photon absorption coefficient at 865 nm can be interpolated from the data in ref to be ∼965 GM.…”

“…It should be noted that the maximum two-photon absorbance of the IR-780 chromophore lies at 875 nm; however, this wavelength is not within the reach of our Ti:Sapphire laser system. The two-photon absorption coefficient at 865 nm can be interpolated from the data in ref to be ∼965 GM.…”

“…The absorption spectrum of the IR-780 dye extends across the UV–vis–NIR region as shown in Figure . It exhibits a series of small bands in the 250–500 nm region, which are associated with higher excited states of polymethine chains. − ,,, The most prominent signal is in the 600–850 nm region and corresponds to the first singlet excited state. This band has a high molar absorptivity coefficient of 274,000 M –1 cm –1 . − ,, On the other hand, several of the higher excited states (S n ( n > 1)) are partially prohibited by one-photon absorption, ,− ,,, which results in low absorption peaks in the region below the first transition wavelength.…”

“…As shown in Figure , in this contribution, we studied antenna-lanthanide complexes, which result from the functionalization of the IR-780 cyanine with phenanthroline or phenyl-terpyridine derivatives, which in turn can coordinate with metallic ions. − This allows for a close interaction between the ion and the organic antenna. A key aspect of the complexes in Figure is the fact that the IR-780 antenna has a higher singlet excited state (S 2 ), which can be populated nonlinearly, thanks to its large two-photon absorption coefficient of up to 2800 GM at 875 nm. , Such large cross section results from the symmetry properties of this state and a near coincidence of: (1) The first cyaninic transition of 1.5 eV and (2) an S 1 –S 2 energy gap of 1.3 eV. With these energy differences, the polymethine chain can be efficiently excited through simultaneous two-photon excitation in the 800–900 nm region.…”