Large Hyperpolarizabilities at Telecommunication-Relevant Wavelengths in Donor-Acceptor-Donor Nonlinear Optical Chromophores.

Abstract

Octopolar D2-symmetric chromophores, based on the MPZnM supermolecular motif in which (porphinato)zinc(II) (PZn) and ruthenium(II) polypyridyl (M) structural units are connected via ethyne linkages, were synthesized. These structures take advantage of electron-rich meso-arylporphyrin or electron-poor meso-(perfluoroalkyl)porphyrin macrocycles, unsubstituted terpyridyl and 4'-pyrrolidinyl-2,2';6',2″-terpyridyl ligands, and modulation of metal(II) polypyridyl-to-(porphinato)zinc connectivity, to probe how electronic and geometric factors impact the measured hyperpolarizability. Transient absorption spectra obtained at early time delays (tdelay < 400 fs) demonstrate fast excited-state relaxation, and formation of a highly polarized T1 excited state; the T1 states of these chromophores display expansive, intense T1 → T n absorption manifolds that dominate the 800-1200 nm region of the NIR, long (μs) triplet-state lifetimes, and unusually large NIR excited absorptive extinction coefficients [ε(T1 → T n ) ∼ 10(5) M(-1) cm(-1)]. Dynamic hyperpolarizability (βλ) values were determined from hyper-Rayleigh light scattering (HRS) measurements, carried out at multiple incident irradiation wavelengths spanning the 800-1500 nm spectral domain. The measured βHRS value (4600 ± 1200 × 10(-30) esu) for one of these complexes, RuPZnRu, is the largest yet reported for any chromophore at a 1500 nm irradiation wavelength, highlighting that appropriate engineering of strong electronic coupling between multiple charge-transfer oscillators provides a critical design strategy to realize octopolar NLO chromophores exhibiting large βHRS values at telecom-relevant wavelengths. Generalized Thomas-Kuhn sum (TKS) rules were utilized to compute the effective excited-state-to-excited-state transition dipole moments from experimental linear-absorption spectra; these data were then utilized to compute hyperpolarizabilities as a function of frequency, that include two- and three-state contributions for both β zzz and β xzx tensor components to the RuPZnRu hyperpolarizability spectrum. This analysis predicts that the β zzz and β xzx tensor contributions to the RuPZnRu hyperpolarizability spectrum maximize near 1550 nm, in agreement with experimental data. The TKS analysis suggests that relative to analogous dipolar chromophores, octopolar supermolecules will be likely characterized by more intricate dependences of the measured hyperpolarizability upon irradiation wavelength due to the interactions among multiple different β tensor components.

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Published Version (Please cite this version)

10.1021/acscentsci.6b00291

Publication Info

Nayak, Animesh, Jaehong Park, Kurt De Mey, Xiangqian Hu, Timothy V Duncan, David N Beratan, Koen Clays, Michael J Therien, et al. (2016). Large Hyperpolarizabilities at Telecommunication-Relevant Wavelengths in Donor-Acceptor-Donor Nonlinear Optical Chromophores. ACS Cent Sci, 2(12). pp. 954–966. 10.1021/acscentsci.6b00291 Retrieved from https://hdl.handle.net/10161/13733.

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Scholars@Duke

Beratan

David N. Beratan

R.J. Reynolds Distinguished Professor of Chemistry

Dr. Beratan is developing theoretical approaches to understand the function of complex molecular and macromolecular systems, including: the molecular underpinnings of energy harvesting and charge transport in biology; the mechanism of solar energy capture and conversion in man-made structures; the nature of charge conductivity in naturally occurring nucleic acids and in synthetic constructs, including the photochemical repair of damaged DNA in extremophiles; CH bond activation by copper oxygenase enzymes; the flow of charge in bacterial appendages on the micrometer length scale; the theoretical foundations for inverse molecular design - the property driven discovery of chemical structures with optimal properties; the exploitation of molecular diversity in the mapping of molecular and materials "space"; the use of infra-red excitation to manipulate electron transport through molecules; the optical signatures of molecular chirality and the influence of chirality on charge transport. Prof. Beratan is affiliated with the Departments of Chemistry, Biochemistry, Physics, as well as Duke's programs in Computational Biology and Bioinformatics, Structural Biology and Biophysics, Nanosciences, and Phononics.  

Therien

Michael J. Therien

William R. Kenan, Jr. Distinguished Professor of Chemistry

Our research involves the synthesis of compounds, supramolecular assemblies, nano-scale objects, and electronic materials with unusual ground-and excited-state characteristics, and interrogating these structures using state-of-the-art transient optical, spectroscopic, photophysical, and electrochemical methods. Over chemical dimensions that span molecules to materials, we probe experimental and theoretical aspects of charge migration reactions and ultrafast electron transfer processes. Insights into the structure-property relationships of molecular, nanoscale, and macroscopic materials allow us to fabricate polarizable and hyperpolarizable chromophores, structures for molecular electronics applications, optical limiters, and a wide range of other electrooptic and photonic materials that include novel conducting polymers, structures for solar energy conversion, and new platforms for in vivo optical imaging. Other efforts in our laboratory involve the elaborating de novo electron- and energy-transfer proteins, interrogating catalytic redox reactions, designing catalysts for small molecule activation, and developing new tools to manipulate nanoscale structures.


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