For the first time, we report the effect of interference between different optical channels on the two-photon absorption (TPA) process in three dimensions. We have employed response theory as well as a sum-over-states (SOS) approach involving few intermediate states to calculate the TPA parameters like transition probabilities (δ TP ) and TPA tensor elements. In order to use the limited SOS approach, we have derived a new formula for a generalized few-state-model (GFSM) in three dimensions. Due to the presence of additional terms related to the angle between different transition moment vectors, the channel interference associated with the TPA process in 3D is significantly different and much more complicated than that in 1D and 2D cases. The entire study has been carried out on the two simplest Reichardt's dyes, namely 2- and 4-(pyridinium-1-yl)-phenolate (ortho- and para-betain) in gas phase, THF, CH 3 CN and water solvents. We have meticulously inspected the effect of the additional angle related terms on the overall TPA transition probabilities of the two 3D isomeric molecules studied and found that the interfering terms involved in the δ TP expression contribute both constructively and destructively as well to the overall δ TP value. Moreover, the interfering term has a more conspicuous role in determining the net δ TP associated with charge transfer transition in comparison to that of π-π* transition of the studied systems. Interestingly, our model calculations suggest that, for o- and p-betain, the quenching of destructive interference associated with a particular two-photon process can be done with high polarity solvents while the enhancement of constructive interference will be achieved in solvents having relatively small polarity. All the one- and two-photon parameters are evaluated using a range separated CAMB3LYP functional. This journal is © the Owner Societies.

M M ALAM

M CHATTOPADHYAYA

S CHAKRABARTI

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Physical Chemistry Chemical Physics

In the present work, we have theoretically studied the one and two-photon absorption (OPA and TPA) probabilities of the native D-luciferin molecule and attempted to find the origin of its larger TPA cross-sections in polar solvents than in non-polar ones. The calculations using state-of-the-art linear and quadratic response theory in the framework of time-dependent density functional theory using hybrid B3LYP functional and cc-pVDZ basis set suggests that two-photon transition probability of this molecule increases with increasing solvent polarity. In order to explicate our present findings, we employed the generalized few-state-model and inspected the role of different optical channels related to the TPA process. We have found that the two-photon transition probability is always guided by a destructive interference term, the magnitude of which decreases with increasing solvent polarity. Furthermore, we have evaluated OPA parameters of D-luciferin and noticed that the the excitation energy is in very good agreement with the available experimental results. © 2016 by the authors; licensee MDPI, Basel, Switzerland. All rights reserved.

Fulltext

Computation

A theoretical study of one-and two-photon activity of D-Luciferin

ConspectusThe two-photon absorption (TPA) process is the simplest and hence the most studied nonlinear optical phenomenon, and various aspects of this process have been explored in the past few decades, experimentally as well as theoretically. Previous investigations have shown that the two-photon (TP) activity of a molecular system can be tuned, and at present, performance-tailored TP active materials are easy to develop by monitoring factors such as length of conjugation, dimensionality of charge-transfer network, strength of donor-acceptor groups, polarity of solvents, self-aggregation, H-bonding, and micellar encapsulation to mention but a few. One of the most intriguing phenomena affecting the TP activity of a molecule is channel interference. The phrase "channel interference" implies that if the TP transition from one electronic state to another involves more than one optical pathway or channel, characterized by the corresponding transition dipole moment (TDM) vectors, the channels may interfere with each other depending upon the angles between the TDM vectors and hence can either increase (constructive interference) or decrease (destructive interference) the overall TP activity of a system to a significant extent. This phenomenon was first pointed out by Cronstrand, Luo, and Ågren [ Chem. Phys. Lett. 2002, 352, 262-269 ] in two-dimensional systems (i.e., only involving two components of the transition moment vectors). For three-dimensional molecules, an extended version of this idea was required. In order to fill this gap, we developed a generalized model for describing and exploring channel interference, valid for systems of any dimensionality. We have in particular applied it to through-bond (TB) and through-space (TS) charge-transfer systems both in gas phase and in solvents with different polarities. In this Account, we will, in addition to briefly describing the concept of channel interference, discuss two key findings of our recent work: (1) how to control the channel interference by chemical means, and (2) the role of channel interference in the anomalous solvent dependence of certain TP chromophores. For example, we will show that simple structurally induced changes in certain dihedral angles of the well-known betaine dye (TB type) will help fine-tune the constructive channel interference and hence increase the overall TP activity of molecules with this general TP channel structure. Another intriguing result we will discuss is observed for a tweezer-trinitrofluorinone complex (TS type) where, on moving from polar to essentially nonpolar solvents, the nature of the channel interference switches from destructive to constructive, leading to a net abnormal solvent dependence of the TP activity of the system. The present Account highlights the usefulness of the channel interference effect and establishes it as a new and unique way of controlling the TP transition probability in different types of three-dimensional molecules. © 2014 American Chemical Society.

Accounts of Chemical Research

Chemical control of channel interference in two-photon absorption processes

We study the effect of donor-acceptor orientation on solvent-dependent three-photon transition probabilities (δ3PA) of representative through-space charge-transfer (TSCT) systems, namely, doubly positively charged [2,2]-paracyclophane derivatives. Our cubic response calculations reveal that the value of δ3PA may be as high as 106 a.u., which can further be increased by a specific orientation of the donor-acceptor moieties. To explain the origin of the solvent cum orientation dependency of δ3PA, we have calculated different three-photon tensor components using a two-state model, noting that only a few tensor elements contribute significantly to the overall δ3PA value. We show that this dependence is due to the large dipole moment difference between the ground and excited states of the systems. The dominance of a few tensor elements indicates a synergistic involvement of π-conjugation and TSCT in the large δ3PA of these systems. © 2013 the Owner Societies.

Effect of donor-acceptor orientation on solvent-dependent three-photon activity in through-space charge-transfer systems-case study of [2,2]-paracyclophane derivatives

In the Letter, we address the question as to why larger two-photon absorption cross sections are observed in nonpolar than in polar solvents for through-space charge-transfer (TSCT) systems such as [2,2]-paracyclophane derivatives. In order to answer this question, we have performed ab initio calculations on two well-known TSCT systems, namely, a [2.2]-paracyclophane derivative and a molecular tweezer-trinitrofluorinone complex, and found that the two-photon transition probability values of these systems decreases with increasing solvent polarity. To rationalize this result, we have analyzed the role of different optical channels associated with the two-photon process and noticed that, in TSCTs, the interference between the optical channels is mostly destructive and that its magnitude increases with increasing solvent polarity. Moreover, it is also found that a destructive interference may sometimes even become a constructive one in a nonpolar solvent, making the two-photon activity of TSCTs in polar solvents less than that in nonpolar solvents. © 2012 American Chemical Society.

Journal of Physical Chemistry Letters

High-Polarity solvents decreasing the two-photon transition probability of through-space charge-transfer systems -A surprising in silico observation

Herein, we show that the two-photon (TP) transition probability (δ TP) of o-betaine system will reach its maximum value at a twist angle around 65°. However, the potential energy scan with respect to the twist angle between its two rings indicates that the molecule in its ground state is quite unstable at this twist angle. Out of the different possibilities, the one having a single methyl group at the ortho position of the pyridinium ring is found to attain the optimum twist angle between the two rings, and interestingly, this particular substituted o-betaine has larger δ TP value than any other substituted or pristine o-betaine. The twist angle dependent variation of δ TP has been explained by employing the generalized-few-state-model formula for 3D molecules. The results clearly reveal that the magnitude of ground to excited state and excited state dipole moment vectors as well as the angle between them are strongly in favor of maximizing the overall δ TP values at the optimum twist angle. The constructive interference between the optical channels at the optimum twist angle also plays an important role to achieve the maximum δ TP value. Furthermore, to give proper judgment on our findings, we have also performed solvent phase calculations on all the model systems in nonpolar solvents, namely, cyclohexane and n-hexane, and the results are quite consistent with the gas phase findings. The present study will definitely offer a new way to synthesize novel two-photon active material based on o-betaine. © 2012 American Chemical Society.

Journal of Physical Chemistry A

Enhancement of twist angle dependent two-photon activity through the proper alignment of ground to excited state and excited state dipole moment vectors

In the present work, we have studied the two-photon absorption (TPA) properties of some selective molecules containing triarylborane and 1-naphthylphenylamine as the acceptor and donor moiety, respectively. The calculations are performed by using the state-of-the-art linear and quadratic response theory in the framework of the time dependent density functional theoretical method. The TPA parameters are calculated with CAMB3LYP functional and the cc-pVDZ basis set. The one-photon results indicate that both the electronic transitions (S0-S1 and S0-S 2) are associated with the charge transfer interaction between the donor and acceptor moieties along with the reorganization of the π-electron density. All these chromophores are found to have very strong two-photon active modes. In order to find out the origin of large TP transition probability of these molecules, we have performed two-state model (TSM) and sum-over-states (SOS) calculations. We have found that the TSM failed to reproduce the correct trend of the TP transition probability of the molecules obtained from the response theory, while SOS is quite successful in doing so. The whole study indicates that the transition moments between the excited states play a pivotal role in controlling the TP transition probabilities of these molecules. The role of solvent in the TP transition probability of these molecules has meticulously been scrutinized within the polarized continuum model (PCM). Further more, we have benchmarked our theoretical findings by calculating the TPA cross-section of a boron and nitrogen containing a charge transfer molecule for which the experimental result is available and we found that our theoretical result is in good agreement with the experimental one which definitely demonstrates the potential of all these light-emitting diode molecules as TP active materials too. © 2011 the Owner Societies.

A critical theoretical study on the two-photon absorption properties of some selective triaryl borane-1-naphthylphenyl amine based charge transfer molecules

We report the highest two-photon absorption cross-section to date, obtained for a molecular tweezer complex. Our analysis suggests that long-range charge-transfer interaction in three dimensions is the main source of this very large two-photon absorption cross section.

Large two-photon absorption cross section: molecular tweezer as a new promising class of compounds for nonlinear optics

In this work, we demonstrate for the first time the importance of weak π-stacking interactions in modulating the two-photon absorption (TPA) process of a fullerene - buckycatcher inclusion complex. To unfold the role of weak interactions on the TPA cross-section, we have used the range-separated Coulomb-attenuating method B3LYP functional (CAMB3LYP) for all time-dependent density functional theory calculations. Our calculations suggest that whereas the buckycatcher has very strong TPA active modes at shorter wavelengths, the TPA modes in the fullerene are very weak but have absorption wavelengths that are in the infrared (IR) or near-IR region of the spectrum. Remarkably, the TPA cross-section of the fullerene - buckycatcher (F - C) supramolecule is quite large at desirable near-IR wavelengths. The overall investigation emphasizes the fact that the limitations of buckycatcher and fullerene as promising TPA active materials can be resolved if one uses the weakly coupled F - C supramolecule instead of considering them individually. © 2009 American Chemical Society.

Journal	Data powered by TypesetPhysical Chemistry Chemical Physics
Publisher	Data powered by TypesetRoyal Society of Chemistry
ISSN	1463-9076