Two-Way Molecular Switches with Large Nonlinear Optical Contrast

Using Femtosecond Laser Pulses to Explore the Nonlinear Optical Properties of Ag/Au Alloy Nanoparticles Synthesized by Pulsed Laser Ablation in a Liquid

Metallic nanoparticles have gained attention in technological fields, particularly photonics. The creation of silver/gold (Ag/Au) alloy NPs upon laser exposure of an assembly of these NPs was described. First, using the Nd: YAG pulsed laser ablation's second harmonic at the same average power and exposure time, Ag and Au NPs in distilled water were created individually. Next, the assembly of Ag and Au NP colloids was exposed again to the pulsed laser, and the effects were examined at different average powers and exposure times. Furthermore, Ag/Au alloy nanoparticles were synthesized with by raising the average power and exposure time. The absorption spectrum, average size, and shape of alloy NPs were obtained by using an ultraviolet-visible (UV-Vis) spectrophotometer and transmission electron microscope instrument. Ag/Au alloy NPs have been obtained in the limit of quantum dots (<10 nm). The optical band gap energies of the Ag/Au alloy colloidal solutions were assessed for different Ag/Au alloy NP concentrations and NP sizes as a function of the exposure time and average power. The experimental data showed a trend toward an increasing bandgap with decreasing nanoparticle size. The nonlinear optical characteristics of Ag/Au NPs were evaluated and measured by the Z-scan technique using high repetition rate (80 MHz), femtosecond (100 fs), and near-infrared (NIR) (750-850 nm) laser pulses. In open aperture (OA) Z-scan measurements, Ag, Au, and Ag/AuNPs present reverse saturation absorption (RSA) behavior, indicating a positive nonlinear absorption (NLA) coefficient. In the close-aperture (CA) measurements, the nonlinear refractive (NLR) indices (n2) of the Ag, Au, and Ag/Au NP samples were ascribed to the self-defocusing effect, indicating an effective negative nonlinearity for the nanoparticles. The NLA and NLR characteristics of the Ag/Au NPs colloids were found to be influenced by the incident power and excitation wavelength. The optical limiting (OL) effects of the Ag/Au alloy solution at various excitation wavelengths were studied. The OL effect of alloy NPs is greater than that of monometallic NPs. The Ag/Au bimetallic nanoparticles were found to be more suitable for optical-limiting applications.

Dynamic effects on the nonlinear optical properties of donor acceptor stenhouse adducts: insights from combined MD + QM simulations

The second-order nonlinear optical (NLO) responses of a donor-acceptor stenhouse adduct (DASA) are investigated by using a computational approach combining molecular dynamics simulations and density functional theory (DFT) calculations. Specific force fields for the open and closed photoswitching forms are first parameterized and validated according to the Joyce protocol, in order to finely reproduce the geometrical features and potential energy surfaces of both isomers in chloroform solution. Then, DFT calculations are performed on structural snapshots extracted at regular time steps of the MD trajectories to address the influence of the thermalized conformational dynamics on the NLO responses related to hyper-Rayleigh scattering (HRS) experiments. We show that accounting for the structural dynamics largely enhances the HRS hyperpolarizability (βHRS) compared to DFT calculations considering solely equilibrium geometries, and greatly improves the agreement with experimental measurements. Furthermore, we show that the NLO responses of the NLO-active open form are correlated with the bond order alternation along the triene bridge connecting the donor and acceptor moieties, which is rationalized using simple essential state models.

Synthesis of Indoles Using the Electrophilic Potential of Diazirines

The electrophilic potential of diazirines has been utilized to obtain N-substituted diaziridines that are directly hydrolyzed to produce monosubstituted hydrazines. The hydrazines can undergo the Fisher process with enolizable carbonyls to yield multiple indole derivatives in moderate to high yields. The N-metalated diaziridine intermediates can undergo isomerization prior to electrophilic substitution, to form N,N-disubstituted hydrazones. The latter react with enolizable carbonyls to produce N-protected indole derivatives in a single step. This protocol was used to efficiently synthesize indomethacin, an anti-inflammatory drug.

Nonlinear Optical Responses of Photoswitchable Donor-Acceptor Stenhouse Adducts

This work combines hyper-Rayleigh scattering (HRS) experiments performed in the NIR range (1.30 and 1.60 μm) and quantum chemical calculations to provide a comprehensive description of the second harmonic generation (SHG) responses of donor-acceptor Stenhouse adducts (DASAs). Representative derivatives of the three generations of DASAs, which differ by the nature of their electron-donating and withdrawing moieties and also include clickable species, have been synthesized and their photoswitching behavior fully characterized. The HRS measurements allow us to establish relationships between the magnitude of the SHG response of open forms and the nature of the donor and acceptor groups. The largest SHG responses are obtained for derivatives incorporating either a barbituric acid or an indanedione acceptor unit, while N-methylaniline appears as the most efficient donor group. The calculations support well the experimental data and show that high hyperpolarizabilities are associated to low excitation energies and large extent of the photoinduced intramolecular charge transfer, which enhances the dipole moment variation between the ground and first dipole-allowed electronic excited state. In addition, a complete investigation of the photoswitching kinetics of DASAs in chloroform solution shows important differences, highlighting in particular the role of the donor group on the photoswitching efficiency.

Designing of gigantic first-order hyperpolarizability molecules via joining the promising organic fragments: a DFT study

A suitable substitution of carbazole with a π-spacer group like cyanoethynylethene offers exciting future opportunities in terms of smart nonlinear optical material. In the quest of better organic nonlinear optical material, we have designed a series of derivatives based on carbazole and cyanoethynylethene fragment combinations in a unique fashion by employing the density functional (DFT) methods. The calculated time-dependent density functional theory (TD-DFT) calculations infer that the gigantic first static hyperpolarizability (β_tot) values are due to a lower energy gap and higher transition dipole moment for the crucial electronic transition. Furthermore, to see the in-depth execution for enhanced second-order nonlinear optics and the structure property relationship on nonlinear optics (NLO) behavior, we have performed frontier molecular orbitals (FMO), density of state (DOS), and transition density matrix (TDM). Furthermore, CAM-B3LYP functional-based calculated results infer that the designed molecule 10 show the first static hyperpolarizability is 923.93 × 10^-30 esu which is 69 times larger than that of p-nitroaniline.

First Hyperpolarizabilities of Intramolecular Charge-Transfer Architectures Based on Acenaphthene Derivatives in Gas, Solution, and Solid States

Constructing charge transfer (CT) systems and packing arrangement are common and effective methods to control the efficiency of nonlinear optical (NLO) materials. Apart from the traditional through-bond CT (TBCT) systems, through-space CT (TSCT) also leads to distinctive optical and electronic properties. Meanwhile, corresponding theoretical investigations of the aggregation effect are highly desired. In this work, some TSCT and model compounds incorporating acenaphthene as a scaffold and triphenylamine (TPA) as the donor are theoretically performed to systematically reveal the effect of both solvent and solid environments on their static first hyperpolarizabilities (β_tot) by using the polarizable continuum model (PCM) and the combined quantum mechanics and molecular mechanics (QM/MM) method. Results indicate that the dichloromethane solvent effect within the PCM approach causes an almost 2 times increase of the β_tot values. Besides, the different packing modes and intermolecular interactions have remarkable influence on the second-order NLO properties. For the case of TPA-ace-CN in the crystal state, the parallel arrangement will lead to large NLO responses (4.9 × 10^-30 esu) compared to the correspondingly isolated molecule (3.4 × 10^-30 esu). However, for the TPA-ace-TRZ compound with the TSCT architecture, selection of the molecular arrangement may make the aggregate ineffective due to the offset of the through-space dipole and charge transfer between D-A groups, which lead to the β_tot values decreasing from 15.2 × 10^-30 to 7.7 × 10^-30 esu. We believe that our calculation will serve as a guide for the exploration of more efficient NLO materials wherein the molecules are oriented in their most favorable arrangements.

Combining Benzazolo-Oxazolidine Twins toward Multi-state Nonlinear Optical Switches

Molecular switches are chemical compounds exhibiting the possibility of reversible transformations between their different forms accompanied by a modification in their properties. Among these, switching of multi-addressable Benzazolo-OXazolidines (BOXs) from a closed form to an open form results in drastic modifications in their linear and nonlinear optical properties. Here, we target molecules containing two identical BOX units (DiBOX) connected by different π-conjugated linkers, and we combine synthesis, UV/visible absorption, and hyper-Rayleigh scattering (HRS) measurements, together with density functional theory (DFT) calculations. Three derivatives have been considered, which differ by the linker: (i) a bithiophene moiety (Bt), (ii) two 3,4-ethylenedioxythiopene (EDOT) units, and (iii) a triad composed of an EDOT-thiophene-EDOT sequence (TtO). As a matter of fact, these systems can adopt three states (CF-CF, POF-POF, and CF-POF) depending on the closed form (CF) or the protonated open form (POF) of each BOX unit. Despite chemical equivalence, stepwise switching of such systems under the addition of a chemical acid or an oxidant has been experimentally evidenced for two of them (DiBOX-Bt and DiBOX-TtO). Then, DFT calculations show that the first BOX opening leads to the formation of a push-pull π-conjugated segment, exhibiting a huge increase in the first hyperpolarizability (β) and a bathochromic shift with respect to the fully closed form. On the contrary, the second BOX opening induces not only a slight bathochromic shift but also a reduction in their β values conferring the great and uncommon abilities to modulate their linear and nonlinear properties over three discrete levels. Among these results, those on DiBOX-Bt agree with the experimental data obtained by HRS measurements and further shed light on their structure-property relationship.

Performance of DFT functionals for calculating the second-order nonlinear optical properties of dipolar merocyanines

Evolution of the static HRS hyperpolarizability of a tricyanopropylidene-based merocyanine dye with the length of the polyenic bridge, as calculated using various ab initio and DFT approximations.

Nonlinear optical properties of spirocyclohexadine photochromes: insights from DFT calculations

The second-order nonlinear optical properties of 1,3-indandione-derived spirocyclohexadine compounds, a new class of photochromes showing sensitivity to both UV and visible lights, are investigated by means of density functional theory. The calculations predict that these compounds should display a large first hyperpolarizability variation upon commutation between their cyclic spiropyran and their merocyanine form. We also show that significant enhancement of the NLO response of the merocyanine form, as well as of the NLO contrast, can be achieved by means of appropriate chemical substitution, which makes these derivatives highly appealing for potential use in photo-responsive NLO devices.

Highly Tunable Multicolor Water-Jet Rewritable Paper Based on Simple New-Type Dual-Addressable Oxazolidines

Rewritable paper based on switchable molecules has attracted great attention in both academic research and marketplace. However, most available switchable dyes have single switchable color state only, which cannot meet the long-awaited multicolor reversible displays. Herein, through simple introduction of phenolic hydroxyl group, we develop a series of new oxazolidines with one switch unit, which could reversibly display two different as well as their mix-gradient colors by treating with water and mild acid, respectively, both in solution and solid substrate. The structures and mechanism for the formation of two colors had been studied in detail via UV-vis/NMR spectroscopy, skillfully designing contrast molecules, and kinetics experiments. This multiple switchable colors of the dyes have been further applied to construct a rewritable paper for ink-free printing with multi/gradient-color display.

Second-order nonlinear optical properties of Stenhouse photoswitches: insights from density functional theory

We report the first investigation of the second-order nonlinear optical (NLO) properties of donor-acceptor Stenhouse adducts (DASAs), an emerging class of colored photochromes that undergo photoswitching with visible light to a colorless form. By using time-dependent density functional theory, we provide insights into the relationships linking the nature of the chemical substituents to the amplitude and contrasts of the NLO response. Solvent and frequency dispersion effects are also analyzed. The calculations predict that DASAs behave as high contrast NLO switches, a finding that extends their potential applications to photo-responsive NLO materials and devices.

Molecular Photoswitching Aided by Excited-State Aromaticity

Central to the development of optoelectronic devices is the availability of efficient synthetic molecular photoswitches, the design of which is an arena where the evolving concept of excited-state aromaticity (ESA) is yet to make a big impact. The aim of this minireview is to illustrate the potential of this concept to become a key tool for the future design of photoswitches. The paper starts with a discussion of challenges facing the use of photoswitches for applications and continues with an account of how the ESA concept has progressed since its inception. Then, following some brief remarks on computational modeling of photoswitches and ESA, the paper describes two different approaches to improve the quantum yields and response times of switches driven by E/Z photoisomerization or photoinduced H-atom/proton transfer reactions through simple ESA considerations. It is our hope that these approaches, verified by quantum chemical calculations and molecular dynamics simulations, will help stimulate the application of the ESA concept as a general tool for designing more efficient photoswitches and other functional molecules used in optoelectronic devices.

Oxazolidine Transient Bases as Molecular Platforms for Testing Dynamic CO2 Capture in Biochemical Systems

Understanding the dynamic processes of CO₂ capture in biosystems is important because of the great effect CO₂ has on the carbon cycle, human health, the global climate, and living environments. After years of multidisciplinary studies, researchers have gained only basic mechanistic knowledge about how enzymes or protein-aggregates capture and deliver CO₂, a process involving reversible bonding of CO₂ with basic amino acid residues. However, vital mechanistic details of how the activated basic residues within these enzymes or protein-aggregates are initially formed, a crucial step for CO₂ capture, are still lacking. Herein, we designed specific molecules, i.e., oxazolidines, which are able to reversibly change their alkalinity via ultrafast isomerizations. Serving as so-called transient bases, these oxazolidines mimic the activated/deactivated states of enzymes or protein-aggregates responsible for dynamic CO₂ capture/release. A detailed mechanism for CO₂ capture, which involves dynamic covalent bonding and multimolecular cooperative interactions among functional groups that occur with the help of a polyhydroxyl environment, is demonstrated by UV-vis and multiple NMR spectroscopies as well as theoretical calculations. Using suitable oxazolidine transient bases, applications for visual CO₂ detection under different detection limit requirements were also developed. Insights for further understanding the process of dynamic CO₂ capture in biosystems are also discussed. This oxazolidine-inspired biomimetic CO₂ capture serves as a platform for the future development of additional biomimicking systems, as well as offers unique perspectives for other complicated life processes.

Three-stage pH-switchable organic chromophores with large nonlinear optical responses and switching contrasts

First three-stage pH-switchable second-order nonlinear optical chromophores are synthesized and characterized by tunable-wavelength (non)linear spectroscopy, showing remarkably different on–off sequences.

Nonlinear optical responses of self-assembled monolayers functionalized with indolino–oxazolidine photoswitches

The second harmonic generation responses of photoresponsive self-assembled monolayers based on indolino–oxazolidine derivatives are computed using a sequential MD/DFT approach.

Second-order nonlinear optical switching with a record-high contrast for a photochromic and thermochromic bistable crystal

Nonlinear optical (NLO) switchable materials are important for photonic and optoelectronic technologies. One important issue for NLO photoswitching, the most studied physical switching approach, is how to improve the switching contrast of second harmonic generation (SHG) in crystals, because the known values are generally below 3 times. Thermoswitching, as another approach, has shown impressive high SHG-switching contrasts (4-∞ times), but the fast decay of thermally induced states demands constant heat sources to maintain specific SHG intensities. We have synthesized a photochromic and thermochromic bistable acentric compound, β-[(MQ)ZnCl3] (MQ+ = N-methyl-4,4'-bipyridinium), which represents the first crystalline compound with both photo- and heat-induced SHG-switching behavior and the first example of a thermoswitchable NLO crystal that can maintain its expected second-order NLO intensity without any heat source. The SHG-switching contrast can reach about 8 times after laser irradiation or 2 times after thermal annealing. The former value is the highest recorded for photoswitchable NLO crystals. This work also indicates that higher SHG-switching contrasts may be obtained through increasing electron-transfer efficiency, variation of permanent dipole moment, and self-absorption.

First hyperpolarizabilities of Pt(4-ethynylbenzo-15-crown-5)2(bpy) derivatives with the complexation of mono-cations (Li+, Na+, K+) and di-cations (Mg2+, Ca2+): development of a cation detector

The coordination of mono-cations and di-cations onto the crown merits the design of the NLO-based cation detector.

A pH-controlled recyclable indolinooxazolidine tagged N-heterocyclic carbene Ru catalyst for olefin metathesis

A pH-controlled recyclable indolinooxazolidine tagged N-heterocyclic carbene Ru catalyst for olefin metathesis has been developed.

Halochromic Isoquinoline with Mechanochromic Triphenylamine: Smart Fluorescent Material for Rewritable and Self-Erasable Fluorescent Platform

Halochromic isoquinoline attached mechanochromic triphenylamine, N-phenyl-N-(4-(quinolin-2-yl)phenyl)benzenamine (PQPBA) and tris(4-(quinolin-2-yl)phenyl)amine (TQPA), smart fluorescent materials exhibit thermo/mechanochromism and tunable solid state fluorescence and their unusual halochromic response in PMMA matrix have been used for fabricating rewritable and self-erasable fluorescent platforms. PQPBA and TQPA showed strong fluorescence in solution (Φ_f = 0.9290 (PQPBA) and 0.9160 (TQPA)) and moderate solid state fluorescence (Φ_f = 20 (PQPBA) and 17% (TQPA). Interestingly, they exhibited a rare temperature (0-100 °C) dependent positive fluorescence enhancement via activating radiative vibrational transition. The deaggregation of PQPBA and TQPA in PMMA polymer matrix lead to the enhancement of fluorescence intensity strongly and fabricated strong blue fluorescent thin films (Φ_f = 58% (PQPBA) and 54% (TQPA). The halochromic isoquinoline has been exploited for demonstrating reversible off-on fluorescence switching by acid (TFA (trifluoroacetic acid)/HCl) and base (NH₃) treatment in both solids as well as PMMA thin films. Importantly, rewritable and self-erasable fluorescent platform has been achieved by make use of unusual fluorescence responses of PQPBA/TQPA with TFA/HCl after exposing NH₃. Single crystal and powder X-ray diffraction (PXRD) studies provided the insight on the solid-state fluorescence and external stimuli-induced fluorescence changes.

The effect of Li doping on the nonlinear optical properties of [2.2]paracyclophane

The similar molecules [2.2]paracyclophane (22PCP) and 1,1,2,2,9,9,10,10-octafluoro[2.2]paracyclophane (8F22PCP) have both generated considerable synthetic interest since they were first prepared. In this work, the nonlinear optical properties of 22PCP, 8F22PCP, and the related Li-doped systems 22PCP-Li and 8F22PCP-Li (which have a Li atom above 22PCP and 8F22PCP, respectively) were investigated. An analysis of natural bond orbital charges showed that there is greater charge transfer from the Li atom to the benzene rings in 8F22PCP-Li than in 22PCP-Li. The variation in the calculated nucleus independent chemical shift (NICS) value as a function of the distance from the lower benzene ring towards the upper benzene ring was found to be W-shaped for both 22PCP and 22PCP-Li. Moreover, whereas all of the NICS values of 22PCP and 22PCP-Li were markedly negative, all of the NICS values of 8F22PCP and 8F22PCP-Li were either positive or only moderately negative. Calculations of the electro-optical properties of these systems showed that the first hyperpolarizability of 22PCP-Li was noticeably larger than that of 8F22PCP-Li. According to the two-level model, the larger first hyperpolarizability of 22PCP-Li is due to its smaller transition energy.

A reduction-responsive polypeptide nanogel encapsulating NIR photosensitizer for imaging guided photodynamic therapy

Internalization of the core-crosslinked nanogel containing a NIR photosensitizer followed by reduction-induced release for both imaging and PDT.

Dye chemistry with time-dependent density functional theory

In this perspective, we present an overview of the determination of excited-state properties of "real-life" dyes, and notably of their optical absorption and emission spectra, performed during the last decade with time-dependent density functional theory (TD-DFT). We discuss the results obtained with both vertical and adiabatic (vibronic) approximations, choosing relevant examples for several series of dyes. These examples include reproducing absorption wavelengths of numerous families of coloured molecules, understanding the specific band shape of amino-anthraquinones, optimising the properties of dyes used in solar cells, mimicking the fluorescence wavelengths of fluorescent brighteners and BODIPY dyes, studying optically active biomolecules and photo-induced proton transfer, as well as improving the properties of photochromes.

Photoisomerization-switchable second-order nonlinear optical responses of dithienylethene-containing boron derivatives: a theoretical study

The switchable second-order nonlinear optical properties of a series of dithienylethene-containing boron compounds possessing reversible photochromic behavior have been systemically investigated based on density functional theory. The significant differences on the static first hyperpolarizabilities caused by the photoisomerization reaction confirm the switchable nonlinear optical behavior. Results show that the closed-ring 1c–4c possess large static first hyperpolarizabilitieswith respect to their corresponding open-ring 1o–4o, which is due to the better π-conjugation and a more obvious degree of charge transfer. Specifically, the static first hyperpolarizability values increase in the range of 2.4–5.2 times with the strengthening electron-withdrawing ability of the substituent R (R = H, CF3, NO2) on the pyridine and elongating the conjugated chains. It indicates that introducing boron-based functional groups to the dithienylethene monomer and modifying the pyridine ring can effectively improve the switching nonlinear optical responses.

One lithium atom binding with P-nitroaniline: lithium salts or lithium electrides?

Recently, both lithium (Li) salts and Li electrides formed by one Li atom interacting with ligand complexes, have been widely investigated. An interesting question emerges: is the configuration of one Li atom interacting with ligand complexes a Li salt or electride? In the present work, four configurations n-Li-PNA (n = 1-4) were obtained by binding one Li atom with the p-nitroaniline (PNA) at different positions to explore this question. The results show that 1-Li-PNA and 2-Li-PNA are typical Li salts, and 4-Li-PNA is a typical Li electride. Significantly, 3-Li-PNA possesses both characteristics of Li salt and electride. At the same time, 3-Li-PNA has the largest first hyperpolarizability (2.9 × 10(6) au) by ROMP2 method compared with the other three configurations. Furthermore, the first hyperpolarizability of 3-Li-PNA is about 2600 times larger than that of PNA. Further, the vertical ionization potential (VIP) and interaction energy (E int) indicate that 3-Li-PNA is less stable than 1-Li-PNA and 2-Li-PNA (Li salts), but is more stable than 4-Li-PNA (Li electrides).

Multiphotochromic molecular systems

We review molecular compounds encompassing several photochromic units with a focus on their functionalities.

Indolinooxazolidine: a versatile switchable unit

The design of multiresponsive systems continues to arouse a lot of interest. In such multistate/multifunctional systems, it is possible to isomerize a molecular system from one metastable state to another by application of different stimulation such as light, heat, proton, or electron. In this context, some researches deal with the design of multimode switch where a same interconversion between two states could be induced by using indifferently two or more different kind of stimuli. Herein, we demonstrate that the association of an indolinooxazolidine moiety with a bithiophene unit allows the development of a new trimode switch. A reversible conversion between a colorless closed form and a colorful open form can be equally performed by light, proton, or electrical stimulation. In addition, the oxidation of this system allows the generation of a third metastable state.

Nonlinear optical molecular switches for alkali ion identification

This work demonstrates by means of DFT and ab initio calculations that recognition of alkali cations can be achieved by probing the variations of the second-order nonlinear optical properties along the commutation process in spiropyran/merocyanine systems. Due to the ability of the merocyanine isomer to complex metal cations, the switching between the two forms is accompanied by large contrasts in the quadratic hyperpolarizability that strongly depend on the size of the cation in presence. Exploiting the nonlinear optical responses of molecular switches should therefore provide powerful analytical tools for detecting and identifying metal cations in solution.

A multistate pH-triggered nonlinear optical switch

By using hyper-Rayleigh scattering experiments and quantum-chemical calculations, we demonstrate that nonlinear optics can be used to probe unequivocally, within a non-destructive process, the multiple electronic states that are activated upon pH- and light-triggered transformations of the 4'-hydroxyflavylium ion. These results open new perspectives in the design of molecular-scale high-density optical memory.

Density functional theory prediction for the second-order nonlinear optical responses of phenanthroline-fused phthalocyanine derivatives

A series of unsymmetrical phenanthroline-fused phthalocyanine derivatives including Zn [ Pc ( Phen )], Zn [ Pc ( Phen )2], Zn [ Pc ( Phen )3], Zn [ Pc ( NH 2)6( Phen )], Zn [ Pc ( NH 2)4( Phen )2], Zn [ Pc ( NH 2)2( Phen )3], Zn [ PcF 6( Phen )], Zn [ PcF 4( Phen )2], and Zn [ PcF 2( Phen )3] were designed to explore their properties of geometric and electronic structures, electronic absorption spectra, and second-order nonlinear responses under density functional theory and time-dependent density functional theory calculations. The computational results show that the peripheral substituents with push-pull effect could obviously change the π–π* transitions, leading to a tunable absorption region in the range between 300–800 nm. The hyperpolarizabilities were carefully investigated using CP-DFT method, revealing the size effect and clarifying the limit when expanding the conjugated system is employed to improve the hyper-Rayleigh scattering response coefficient (βHRS). According to the results, the NH 2-substitued phenanthroline-fused phthalocyanines are considered as ideal NLO blocking materials with large βHRS.