Correlation studies on structurally diverse porphyrin monomers, dimers and trimers and their nonlinear optical responses

Abstract

GRAPHICAL ABSTRACT Pictogram SynopsisThe nonlinear optical absorption of porphyrins can be modulated via chemical modifications of the ring system and the regiochemical arrangement of the substituents. ACCEPTED MANUSCRIPT ABSTRACTAn investigation of the nonlinear absorption of a wide range of structurally diverse porphyrin monomers, bisporphyrins and trisporphyrins, using open Z-scan technique with 6 ns pulsed laser operating at 532 nm was carried out. Using the theory of reverse saturable absorption, the intensity dependent nonlinear absorption coefficient eff was deduced from the experiments. Monomers which Soret band maximum was situated closer to the experimental wavelength had higher eff . The eff of dimers and trimers were in the same range as for monomers. The highest eff = 5.3 10 -8 cmW -1 was found for a zinc complex of 5,15-A 2 B 2 type porphyrins with 3-methoxyphenyl and trimethylsilyl-ethynyl groups in the meso positions.

Nonlinear absorption properties of 5,10-A2B2porphyrins—correlation of molecular structure with the nonlinear responses

“…We noted a similar trend for structurally diverse porphyrins of the 5,15-A 2 B 2 , 5,15-A 2 BC series before. 14,36 The same observation can be applied to the 5,10-A 2 B 2 compounds studied, i.e., both κ 1 and κ 2 increase with the maximum of the Soret band. …”

“…The values of β eff obtained were comparable to those reported before for phthalocyanines and porphyrins. 14,30,32 All of the recorded responses, at a whole range of input energies, were successfully fitted with the four-level model. The model assumes consecutive one-and two-photon excited state absorption (one-+ one-+ two-photon absorption).…”

“…Based on previous studies in which we identified {5,15-bis-(3-methoxyphenyl)-10,20-di[(trimethylsilyl)ethynyl]porphyrinato}-zinc(II) as the most promising among numerous porphyrins with varied meso substituents 14 and the literature indicated the utility of lead porphyrins with (trimethylsilyl)ethynyl (TMSethynyl) groups, 7 thus, we decided to further explore the potential of the very promising TMS-ethynyl substituent in the context of 5,10-A 2 B 2 porphyrins.…”

“…A standard means of Z-scan trace analysis, broadly applied in the literature, involves fitting of the experimental data with the analytical expression for the normalized transmission as a function of sample's position along the Z-axis to extract effective nonlinear absorption coefficient β eff , which is used for comparative studies. 14,30 It should be mentioned that β eff is not a molecular quantity and thus is expected to depend on concentration and path length (herein, the same experimental conditions were applied for all experiments). The procedure for β eff extraction was used to fit the recorded NLA responses.…”

“…5,11,12 Most studies focused on highly symmetric meso tetrasubstituted compounds and a few reports on meso and β-substituted compounds or 5,15-A 2 B 2 -type porphyrins have been published. 13,14 Most studies investigated either substituent or central metal effects on the OL performance. Still, consistent structure-OL performance relationships are not yet in hand.…”