Solid-state Optical Properties Research Articles

1,2,3-Triazol-5-ylidene- vs. 1,2,3-triazole-based tricarbonylrhenium(I) complexes: influence of a mesoionic carbene ligand on the electronic and biological properties.

The tricarbonylrhenium complexes that incorporate a mesoionic carbene ligand represent an emerging and promising class of molecules, the solid-state optical properties of which have rarely been investigated. The aim of this comprehensive study is to compare three of these complexes with their 1,2,3-triazole-based analogues. The Hirshfeld surface analysis of the crystallographic data revealed that the triazolylidene derivatives are more prone to π-π interactions than their 1,2,3-triazole-based counterparts. The FT-IR and electrochemical data indicated a stronger electron donor effect from the organic ligand to the rhenium atom for triazolylidene derivatives, which was confirmed by DFT calculations. All compounds were phosphorescent in solution, where the 1,2,3-triazole-based complexes showed unusually strong dependence on dissolved oxygen. All compounds also emitted in the solid state, some of them exhibited marked solid-state luminescence enhancement (SLE) effect. The 1,2,3-triazole based complex Re-Phe even displayed astounding photoluminescence efficiency with quantum yield up to 0.69, and proved to be an excellent candidate for applications linked to aggregation-induced emission (AIE). Interestingly, one triazolylidene-based complex (Re-T-BOP) showed attractive antibacterial activity. This study highlights the potential of these new molecules for applications in the fields of photoluminescent and therapeutic materials, and provides the first bases for the design of efficient molecules in these research areas.

Nonaxisymmetrical 9,10-diarylanthracenes: Separable swivel conformers and promising optoelectronic properties

The chemical and physical functions of organic molecules are closely related to their conformations in both solutions and solid states, but the successful separation of organic conformers is usually very difficult because of the rapid internal rotation of single bonds. In the current work, we first demonstrate two stable and separable conformers with swivel cross-conjugated configuration based on 9,10-diphenylanthracene derivatives, and they are confirmed by 1H NMR spectra and single crystal analysis. The introduction of two bulky groups at the ortho positions of the two phenyls can enhance the internal rotation barrier of phenyl–anthryl single bond to fully stabilize the conformers in respective conformation even in reflux toluene. We find that they show similar solution but very different solid-state optical properties such as different emission wavelength and fluorescence efficiency. Moreover, only the syn conformer crystal can exhibit mechanochromic luminescence and mechanoluminescence.

Luminescent fac-[ReX(CO)3(phenyl-pyta)] (X = Cl, Br, I) complexes: influence of the halide ligand on the electronic properties in solution and in the solid state.

Tricarbonylrhenium(I) complexes that incorporate a chloride ligand are promising photoluminescent materials, but those incorporating a bromide or iodide ligand have received very little attention regarding their solid-state properties. In this work, three rhenium(I) complexes differing only by the nature of their halide ligand (X = Cl, Br, and I) were compared. They are based on a fac-[ReX(CO)3(N^N)] framework where the N^N bidentate ligand is a 3-(2-pyridyl)-1,2,4-triazole unit functionalized by an appended phenyl group. DFT calculations showed that the character of the lowest energy transitions progressively changes from Re → N^N ligand (MLCT) to X → N^N ligand (XLCT) when increasing the size of the halogen atom. Regarding the electrochemical behavior, the chloride and bromide complexes 1-Cl and 1-Br were similar, while the iodide complex 1-I exhibited a strikingly different electrochemical signature in oxidation. From a spectroscopic viewpoint, all three complexes emitted weak red-orange phosphorescence in dichloromethane solution. However, in the solid state, marked differences appeared. Not only was 1-Cl a good emitter of yellow light, but it had strong solid-state luminescence enhancement (SLE) properties. In comparison, 1-Br and 1-I were less emissiveand they showed better mechanoresponsive luminescence (MRL) properties, probably related to a loose molecular arrangement in the crystal packing and to the opening of vibrational non-radiative deactivation pathways. This study highlights for the first time how the nature of the halide ligand in this type of complex allows fine tuning of the solid-state optical properties, for potential applications either in bio-imaging or in the field of MRL-active materials.

Homochiral coordination polymers of Zn(II) and Pb(II) with interesting three-dimensional helicates

Based on a designed enantiomerically pure chiral ligand H3L, two interesting homochiral metal−organic frameworks (HMOFs), namely {[Zn3(L)2(H2O)2]∙2H2O}n (1) and {[Pb(HL)(H2O)]∙H2O}n (2), have been solvothermally synthesized (H3L = (S)-4'-(((1-carboxyethyl)amino)methyl)-[1,1′-biphenyl]-3,5-dicarboxylic acid). Complexes 1 and 2 are novel three-dimensional metal−organic helicates with different structural motifs. In 1, anionic (L)3− ligands bridge trimetallic Zn-clusters to form a [3,6]-connected architecture of (63)2(612·83) topology. In particular, each trimetallic Zn-cluster is the node of six strand 21 helical chains consisting of four right-handed helical chains and two left-handed helical chains. In 2, zwitterionic (HL)2− ligands link PbII ions into a 3-connected 103-topological helicate composed of 21 helical chains extending along three crystal axes, and two thirds of which are left-handed. Interesting enough, the chiral ligand H3L not only transferred its inherent chirality to the synthesized complexes 1 and 2, but also induced unexpected helical chirality. Furthermore, the morphologies, thermal stabilities and solid-state optical properties including CD spectra, and nonlinear optical and luminescent properties of compounds 1 and 2 were also carried out. Compounds 1 and 2 exhibit interesting fluorescence emissions and obvious second-order nonlinear activity in addition to the excellent thermal stability of their dehydrated frameworks, indicating that the HMOF materials have great potential in optical devices.

Thin-Film Morphology and Optical Properties of Photoisomerizable Donor-Acceptor Oligothiophenes.

It was recently reported that the most popular electron-accepting units introduced to π-conjugated oligomers studied for organic photovoltaic applications are susceptible to unwanted and even destructive photochemical reactions. The consequences of Z/E photoisomerization of the popular 2-(1,1-dicyanomethylene)rhodanine (RCN) unit on the optical and morphological properties of a homologous series of RCN-functionalized oligothiophenes are studied here. Oligomers consisting of one, two, or three thiophene units were studied as pure Z isomers and with E isomer compositions of 25, 53, and 45%, respectively, for Z/E mixtures. Solutions of Z isomers and Z/E mixtures were characterized by UV-vis and photoluminescence spectroscopy, wherein changes to optical properties were evaluated on the basis of E isomer content. X-ray diffraction of thin-film Z/E mixtures reveals crystalline domains of both Z and E forms after thermal annealing for mono- and bithiophene oligomers, with greater interplanar spacing for E crystalline domains than the Z counterparts along the substrate normal direction. The surface morphology viewed by atomic force microscopy also shows fiberlike structures for the E form with a much larger aspect ratio than for the Z domains in the bithiophene oligomer. Optical characterization reveals drastic changes in the solid state upon introduction of the E form for the mono- and bithiophene derivatives, whereas subtle consequences are noted for the terthiophene analogue. Most notably, a 132 nm redshift in maximum absorption occurs for the bithiophene oligomer films containing 53% E isomer compared to the pure Z counterpart. Finally, although solid-state photoisomerization experiments find no evidence of Z → E isomerization in polycrystalline Z films, E → Z isomerization is observed and becomes more restrictive in films with higher crystallinity (i.e., after thermal annealing). This structure-property study, which elucidates the consequences of the RCN configuration on solid-state packing and optical properties, is expected to guide the development of more efficient and stable organic optoelectronic devices.

Solution and Solid-State Optical Properties of Trifluoromethylated 5-(Alkyl/aryl/heteroaryl)-2-methyl-pyrazolo[1,5-a]pyrimidine System

This paper describes the photophysical properties of a series of seven selected examples of 5-(alkyl/aryl/heteroaryl)-2-methyl-7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidines (3), which contain alkyl, aryl, and heteroaryl substituents attached to the scaffolds of 3. Given the electron-donor groups and -withdrawing groups, the optical absorption and emission in the solid state and solution showed interesting results. Absorption UV–Vis and fluorescence properties in several solvents of a pyrazolo[1,5-a]pyrimidines series were investigated, and all derivatives were absorbed in the ultraviolet region despite presenting higher quantum emission fluorescence yields in solution and moderate emission in the solid state. Moreover, the solid-state thermal stability of compounds 3a–g was assessed using thermogravimetric analysis. The thermal decomposition profile showed a single step with almost 100% mass loss for all compounds 3. Additionally, the values of T0.05 are considerably low (72–187 °C), especially for compound 3a (72 °C), indicating low thermal stability for this series of pyrazolo[1,5-a]pyrimidines.

Perilen Diimid Türevlerinin Uyarılmış Hal Özelliklerine İmid İkamelerinin Etkisi

Solid state optical properties of fluorescent materials are important for many optical and electronic photonic devices such as organic light emitting diodes, frequency down-converters or luminescent solar concentrators. Perylene diimides (PDIs) represent one of the most popular organic semiconductors which find application in those phonic device applications. In this study, photophysical properties of two dibrominated PDI (DiBrPDIs), one of which contains a branched alkyl chain (2-ethylhexyl, 2-EH) and the other has an aromatic substituent (diisopropylphenyl, DIA) at the imide positions are comparatively studied. Besides their absorption and photoluminescence, lifetime and photoluminescence quantum yield (PLQY), photoinduced absorption properties (PIA) were also examined by fs-transient absorption spectroscopy. Due to their the same π conjugated system, DiBrPDI-DIA and DiBrPDI-2EH exhibited identical absorption and photoluminescence (PL) spectra in solution phase (λabs:527 nm and λPL:552 nm). However, in their film phases which were prepared at the same conditions, DiBrPDI-DIA (λPL-DIA:596 nm; PLQY:73.4%) presented a shorter PL wavelength with a higher PLQY than that of DiBrPDI-2EH (λPL-2EH:649 nm; PLQY:36.7%). 3-D investigations performed by using Chem3D pro software addressed the higher intermolecular distance between the perylene rings induced by the bulky DIA groups, as the main reason of this difference.

Solid-state optical properties of self-assembling amyloid-like peptides with different charged states at the terminal ends

The self-assembling of small peptides not only leads to the formation of intriguing nanoarchitectures, but also generates materials with unexpected functional properties. Oligopeptides can form amyloid-like cross-β assemblies that are able to emit intrinsic photoluminescence (PL), over the whole near-UV/visible range, whose origin is still largely debated. As proton transfer between the peptide chain termini within the assembly is one of the invoked interpretations of this phenomenon, we here evaluated the solid state PL properties of a series of self-assembled hexaphenylalanine peptides characterized by a different terminal charge state. Overall, our data indicate that the charge state of these peptides has a marginal role in the PL emission as all systems exhibit very similar multicolour PL associated with a violation of the Kasha’s rule. On the other hand, charged/uncharged ends occasionally produce differences in the quantum yields. The generality of these observations has been proven by extending these analyses to the Aβ16–21 peptide. Collectively, the present findings provide useful information for deciphering the code that links the spectroscopic properties of these assemblies to their structural/electronic features.

Air-Stable Thermoluminescent Carbodicarbene-Borafluorenium Ions.

Borenium ions, originally synthesized as fundamentally important laboratory curiosities, have attracted significant attention due to their applications in catalysis and frustrated Lewis pair chemistry. However, investigations of the materials properties of these types of compounds are exceptionally rare. Herein, we report the synthesis, molecular structures, and optical properties of a new class of air-stable borenium ions, stabilized by the strongly donating carbodicarbene (CDC) ligand (2, 3, 6). Notably, CDC-borafluorenium ions exhibit thermoluminescence in solution, a result of a twisted intramolecular charge transfer process. The temperature responsiveness, which is observable by the naked eye, is assessed over a 20 to -60 °C range. Significantly, compound 2 emits white light at lower temperatures. In the solid state, these borocations exhibit increased quantum yields due to aggregation-induced emission. CDC-borafluorenium ions with two different counteranions (Br-, BPh4-) were investigated to evaluate the effect of anion size on the solution and solid-state optical properties. In addition, CDCs containing both symmetrical and unsymmetrical N-heterocycles (bis(1-isopropyl-3-methylbenzimidazol-2-ylidene)methane and bis(1,3-dimethyl-1,3-dihydro-2H-benzo[d]imidazol-2-ylidene)methane) were tested to understand the implications of free rotation about the CDC ligand carbon-carbon bonds. The experimental work is complemented by a comprehensive theoretical analysis of the excited-state dynamics.

Structural evolution of carbon dots during low temperature pyrolysis.

Carbon dots (CDs) are an emerging class of photoluminescent material. Their unique optical properties arise from the discrete energy levels in their electronic states, which directly relate to their crystalline and chemical structure. It is expected that when CDs go through structural changes via chemical reduction or thermal annealing, their energy levels will be altered, inducing unique optoelectronic properties such as solid-state photoluminescence (PL). However, the detailed structural evolution and how the optoelectronic characteristics of CDs are affected remain unclear. Therefore, it is of fundamental interest to understand how the structure of CDs prepared by hydrothermal carbonisation (HTC) rearranges from a highly functionalised disordered structure into a more ordered graphitic structure. In this paper, detailed structural characterisation and in situ TEM were conducted to reveal the structural evolution of CDs during the carbonisation process, which have demonstrated a growth in aromatic domains and reduction in oxidation sites. These structural features are correlated with their near-infrared (NIR) solid-state PL properties, which may find a lot of practical applications such as temperature sensing, solid-state display lighting and anti-counterfeit security inks.

A new two-dimensional homochiral cadmium(II) coordination polymer: synthesis, structure determination, optical properties, and fluorescent sensing

A new two-dimensional (2D) homochiral cadmium(II) coordination polymer, {[Cd4(OH)2(L)2(pea)4]·CH3OH} n (1) (pea = (S)-1-phenylethanamine), was solvothermally synthesized based on an enantiomerically pure chiral ligand (S)-5-(((1-carboxy-2-phenylethyl)amino) methyl)isophthalic acid (H3L). Crystal structure analysis shows that 1 is a 2D homochiral framework consisting of coaxial double-helical chains where a pair of left- and right-handed 21 helixes shares tetranuclear Cd cluster subunits [Cd4(μ 3-OH)2]. Topologically, 1 is an interesting 3,6-connected network with the point symbol of (43)2(46·66·83). The thermal stability and solid-state optical properties, including circular dichroism, and nonlinear optical and luminescent properties of 1 were systematically investigated. Furthermore, the fluorescence response of 1 to various common solvents and metal ions was preliminarily studied. Interesting enough, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), acetone and Fe3+ ion have strong quenching effect on the fluorescence of 1, indicating that 1 has certain potential application in the visual detection of these species.

Structure–Assembly–Property Relationships of Simple Ditopic Hydrogen-Bonding-Capable π-Conjugated Oligomers

A series of simple ditopic hydrogen-bonding-capable molecules functionalized with 2,4-diamino-1,3,5-triazine (DAT), barbiturate (B), and phthalhydrazide (PH) on both termini of a 2,2′-bithiophene linker were designed and synthesized. The intrinsic electronic structures of the ditopic DAT, PH, and B molecules were investigated with ground-state density functional theory calculations. Their solution absorbance was investigated with UV-vis, where it was found that increasing size of R group substituents on the bithiophene linker resulted in a general blue-shift in solution absorbance maximum. The solid-state optical properties of ditopic DAT and B thin films were evaluated by UV-vis, and it was found that the solid-state absorbance was red-shifted with respect to solution absorbance in all cases. The three DAT molecules were vacuum-thermal-deposited onto Au(111) substrates and the morphologies were examined using scanning tunneling microscopy. (DAT-T)2 was observed to organize into six-membered rosettes on the surface, whereas (DAT-TMe)2 formed linear assemblies before and after thermal annealing. For (DAT-Toct)2 , an irregular arrangement was observed, while (B-TMe)2 showed several co-existent assembly patterns. The work presented here provides fundamental molecular–supramolecular relationships useful for semiconductive materials design based on ditopic hydrogen-bonding-capable building blocks.

Cyano-substituted oligo(p-phenylene-vinylene)s having linear and branched octyloxy groups: control of aggregation and emission properties via C8 alkyl chain difference

Alkyl chain structures, linear and branched C8, induced the tuning of H- and J-aggregation, resulting in different solid-state optical properties.

Modulation of Solid-State Optical Properties of o-Hydroxynaphthoic Acids through Formation of Charge Transfer Cocrystals with TCNB

Charge transfer cocrystals offer an opportunity to alter the photophysical characteristics of organic chromophores in the solid state. A set of new charge transfer cocrystals of three positional is...

Dipyrrolyldiketonato Titanium(IV) Complexes from Monomeric to Multinuclear Architectures: Synthesis, Stability, and Liquid-Crystal Properties.

Dipyrrolyldiketone ligands (dpkH) are used with Ti(OiPr)4 to afford monomeric titanium(IV) complexes displaying the general formula C2-[Ti(dpk)2(OiPr)2]. The dpkH ligands employed consist of two dipyrrolyldiketone compounds (2H and 3H) and three diphenyl-substituted analogues (4H-6H). The behavior of these octahedral [Ti(dpk)2(OiPr)2] species in solution was investigated by 1H NMR at variable temperatures. Dynamic phenomena were evidenced, and the activation parameters associated with these processes (ΔH⧧, ΔS⧧, and ΔG⧧) were retrieved. [Ti(dpk)2(OiPr)2] complexes are precursors for the formation of high-nuclearity aggregates whose structures depend on the substituents on the diketone backbone. The crystal structures of monomeric ([Ti(1)2(OiPr)2]; 1 is the 1,3-diphenyl-1,3-propanedionato ligand) and [Ti(2)2(OEt)2]), dimeric ([Ti2(1)4(μ2-O)2]), and tetrameric ([Ti4(4)8(μ2-O)4]) species have been established, and the origin of this structural diversity is discussed. The solid-state optical properties of several complexes were determined and interpreted with the help of DFT calculations. Finally, the dinuclear complex [Ti(6)2(μ2-O)2] was synthesized, where ligand 6 incorporates six long alkyl chains (C16H33). This complex shows rich mesomorphic properties, with an original room-temperature plastic crystal phase followed by a hexagonal columnar liquid-crystalline phase.

Homochiral lanthanide metal–organic frameworks based on amino acid-functionalized terpyridyl ligand: synthesis, structure determination, and optical properties

Utilizing chiral terpyridine derivative ligand (S)-2-((4-([2,2′:6′,2″-terpyridin]-4′-yl)benzyl)amino)propanoic acid (HL) and corresponding Ln(NO3)3, five new isostructural homochiral lanthanide metal–organic frameworks [{[Ln2(HL)2(NO3)4(H2O)4]·NO3·Cl·7H2O}n [Ln = Nd (1), Pr (2), Sm (3), Eu (4), Tb (5)] comprised of left- and right-handed helical chains were solvothermally synthesized. Various means such as IR spectroscopy, elemental analysis, powder X-ray diffraction, and thermal analysis were used to characterize the compounds, wherein compounds 1 and 2 were crystallographically characterized. In the structure of representative 1, zwitterionic ligands HL bridge Nd3+ ions through the monodentate coordination of their carboxylates and the tridentate chelation of their terpyridyls, leading to the formation of left- and right-handed helical chains. The adjacent left- and right-handed helical chains are further connected into a 2D helical layer through interchain hydrogen-bonding interactions, and these layers stack up through interlayer π⋯π interactions to form an interesting three-dimensional homochiral cationic architecture with one-dimensional triangular channels wherein guests anions and water are trapped. The compounds were systematically studied with respect to their solid-state optical properties, including CD spectra, and nonlinear optical and luminescent properties, and the results showed that the sensitization effect of HL ligand on the emission of Tb3+ and Eu3+ was better than that of Sm3+.

Dielectric and magnetic properties of InCr1−xTixO3+x/2 (x = 3/4, 5/7 and 2/3) solid solution

Single-phase samples of InCr1−xTixO3+x/2 with x = 3/4, 5/7 and 2/3 compositions were synthesized by the solid-state reaction method, and optical, dielectric and magnetic properties were explored for the first time. Crystal structure analysis showed a complete Cr3+/Ti4+ solubility, and the monoclinic crystal structure was successfully characterized. The optical bandgap was obtained by both Kubelka–Munk function and Tauc plot method. The Cr3+/Ti4+ composition has a little effect in the direct bandgap taking values of 2.09 eV for x = 3/4 and 1.97 eV for x = 2/3, respectively. We found that the permittivity shows a peak strongly dependent on the frequency, which is typical of relaxor behavior. In addition, the relaxor peak is dependent on the Cr3+/Ti4+ composition. The AC conductivity analysis showed that main charge carriers to participate in the electric conductivity are associated with small polarons with Eact ~ 0.40 eV. Diluted magnetic or paramagnetic behavior was found in the magnetization studies. Accordingly, we found that the compositional disordered Cr3+/Ti4+ cations randomly distributed among equivalent sites into Cr/Ti–O layer explain both the dielectric relaxor and magnetic features.

Synthesis, crystal structures and solid-state optical properties of two Mannich derivatives of 2’,7’-dichlorofluorescein

Synthesis, crystal structures and solid-state optical properties of two Mannich derivatives of 2’,7’-dichlorofluorescein

Homochiral Metal–Organic Frameworks of Lead(II) and Cadmium(II) Constructed by Amino Acid-Functionalized Isophthalic Acids: Synthesis, Structure Diversity, and Optical Properties

On the basis of amino acid-functionalized isophthalic acids, four interesting homochiral metal–organic frameworks (HMOFs), namely, {[Pb2(HL1)2]·11H2O}n (1), {[Pb2(HL2)2]·12H2O}n (2), {[Cd6(L2)4(H2O)11]·6H2O}n (3), and [Pb(HL3)]n (4), were constructed (H3L1 = (S)-5-(((1-carboxyethyl)amino)methyl)isophthalic acid, H3L2 = (S)-5-(((1-carboxy-3-methylbutyl)amino)methyl)isophthalic acid, and H3L3 = (S)-5-(((1-carboxy-2-phenylethyl)amino)methyl)isophthalic acid). In 1, 2, and 4, all PbII ions have hemidirected coordination geometries despite the difference in coordination number, and ligands H3L1–H3L3 in negative bivalent zwitterionic forms adopt various coordination modes to bridge PbII centers into two- and three-dimensional (2D–3D) coordination polymers, respectively. Both 1 and 2 contain two independent 63-topological homochiral layers which further form a unique hydrogen-bonded double-layered HMOF with the stereochemically active lone pairs of all PbII ions pointing inward and the hydrophobic side arms of amino acid groups being located on both sides. For 4, it is a 3D helicate of (42·6·83)(42·63·8) topology, and the resulting one-dimensional (1D) channels are occupied by the hydrophobic benzyls of amino acid groups in (HL3)2– ligands. Coordination polymer 3 is an intriguing HMOF that contains two independent 2D double-layered (63)(65·8)-topological helicates with alternating distribution of 1D hydrophilic and hydrophobic helical channels. In 3, all hydrophilic helical channels are occupied by water molecules, while all hydrophobic helical channels are filled by the isobutyls of amino acid groups. Remarkably, these chiral tricarboxylic ligands not only have versatile coordination modes in the construction of HMOFs, but also subtly regulate the crystal structures through the different hydrophobic side arms of amino acids implanted in these ligands. Furthermore, the thermal stabilities and solid-state optical properties, including CD spectra, and nonlinear optical and luminescent properties of these complexes were also investigated. Interestingly enough, in our example, it was found that hemidirected, five-coordinate PbII compounds perhaps have stronger emission than those hemidirected four- or six-coordinate PbII compounds.

Solid-State Nonlinear Optical Properties of Mononuclear Copper(II) Complexes with Chiral Tridentate and Tetradentate Schiff Base Ligands.

Salen-type metal complexes have been actively studied for their nonlinear optical (NLO) properties, and push-pull compounds with charge asymmetry generated by electron releasing and withdrawing groups have shown promising results. As a continuation of our research in this field and aiming at solid-state features, herein we report on the synthesis of mononuclear copper(II) derivatives bearing either tridentate N2O Schiff bases L(a−c)− and pyridine as the forth ancillary ligand, [Cu(La−c)(py)](ClO4) (1a–c), or unsymmetrically-substituted push-pull tetradentate N2O2 Schiff base ligands, [Cu(5-A-5′-D-saldpen/chxn)] (2a–c), both derived from 5-substituted salicylaldehydes (sal) and the diamines (1R,2R)-1,2-diphenylethanediamine (dpen) and (1S,2S)-1,2-diaminocyclohexane (chxn). All compounds were characterized through elemental analysis, infrared and UV/visible spectroscopies, and mass spectrometry in order to guarantee their purity and assess their charge transfer properties. The structures of 1a–c were determined via single-crystal X-ray diffraction studies. The geometries of cations of 1a–c and of molecules 2a–c were optimized through DFT calculations. The solid-state NLO behavior was measured by the Kurtz–Perry powder technique @1.907 µm. All chiral derivatives possess non-zero quadratic electric susceptibility (χ(2)) and an efficiency of about 0.15–0.45 times that of standard urea.