Tomasz Seidler

Evaluation of the Linear and Second-Order NLO Properties of Molecular Crystals within the Local Field Theory: Electron Correlation Effects, Choice of XC Functional, ZPVA Contributions, and Impact of the Geometry in the Case of 2-Methyl-4-nitroaniline.

The linear [χ((1))] and second-order nonlinear [χ((2))] optical susceptibilities of the 2-methyl-4-nitroaniline (MNA) crystal are calculated within the local field theory, which consists of first computing the molecular properties, accounting for the dressing effects of the surroundings, and then taking into account the local field effects. Several aspects of these calculations are tackled with the aim of monitoring the convergence of the χ((1)) and χ((2)) predictions with respect to experiment by accounting for the effects of (i) the dressing field within successive approximations, of (ii) the first-order ZPVA corrections, and of (iii) the geometry. With respect to the reference CCSD-based results, besides double hybrid functionals, the most reliable exchange-correlation functionals are LC-BLYP for the static χ((1)) and CAM-B3LYP (and M05-2X, to a lesser extent) for the dynamic χ((1)) but they strongly underestimate χ((2)). Double hybrids perform better for χ((2)) but not necessarily for χ((1)), and, moreover, their performances are much similar to MP2, which is known to slightly overestimate β, with respect to high-level coupled-clusters calculations and, therefore, χ((2)). Other XC functionals with less HF exchange perform poorly with overestimations/underestimations of χ((1))/χ((2)), whereas the HF method leads to underestimations of both. The first-order ZPVA corrections, estimated at the B3LYP level, are usually small but not negligible. Indeed, after ZPVA corrections, the molecular polarizabilities and first hyperpolarizabilities increase by 2% and 5%, respectively, whereas their impact is magnified on the macroscopic responses with enhancements of χ((1)) by up to 5% and of χ((2)) by as much as 10%-12% at λ = 1064 nm. The geometry plays also a key role in view of predicting accurate susceptibilities, particularly for push-pull π-conjugated compounds such as MNA. So, the geometry optimized using periodic boundary conditions is characterized by an overestimated bond length alternation, which gives larger molecular properties and even larger macroscopic responses, because of the local field factor amplification effects. Our best estimates based on experimental geometries, charge dressing field, ZPVA correction, and CCSD molecular properties lead to an overestimation of χ((1)) by 12% in the static limit and 7% at λ = 1064 nm. For χ((2)), the difference, with respect to the experiment, is satisfactory and of the order of one standard deviation.

Investigation of the linear and second-order nonlinear optical properties of molecular crystals within the local field theory.

In this paper it is shown that modest calculations combining first principles evaluations of the molecular properties with electrostatic interaction schemes to account for the crystal environment effects are reliable for predicting and interpreting the experimentally measured electric linear and second-order nonlinear optical susceptibilities of molecular crystals within the experimental error bars. This is illustrated by considering two molecular crystals, namely: 2-methyl-4-nitroaniline and 4-(N,N-dimethylamino)-3-acetamidonitrobenzene. Three types of surrounding effects should be accounted for (i) the polarization due to the surrounding molecules, described here by static electric fields originating from their electric dipoles or charge distributions, (ii) the intermolecular interactions, which affect the geometry and particularly the molecular conformation, and (iii) the screening of the external electric field by the constitutive molecules. This study further highlights the role of electron correlation on the linear and nonlinear responses of molecular crystals and the challenge of describing frequency dispersion.

The crystal structure and optical properties of a pharmaceutical co-crystal – the case of the melamine–barbital addition compound

The melamine barbital co-crystal is a product of crystal engineering of non-linear optical materials composed of pharmaceutically active ingredients. The resulting crystal phase shows a non-linear effect higher than that of KDP. The material was characterized by means of X-ray diffraction and optical property measurements and calculations.

N-(5-Nitro­pyridin-2-yl)-5H-dibenzo[d,f][1,3]diazepine-6-carboxamide

The title compound, C19H13N5O3, can be obtained from the corresponding α-amido-α-aminonitrone in a reaction with biphenyl-2,2′-diamine. The amido–amidine core has distinctive geometrical parameters including: an outstandingly long Csp 2—Csp 2 single bond of 1.5276 (13) Å and an amidine N—C—N angle of 130.55 (9)°. Intramolecular N—H⋯O, N—H⋯N and C—H⋯O hydrogen bonds occur. In the crystal, molecules form layers parallel to (001) via weak intermolecular C—H⋯N interactions. The layers are linked via N—H⋯O hydrogen bonds and π–π interactions along [001] [benzene–pyridine centroid–centroid distance = 3.672 (2) Å].

Erratum: “Linear and second-order nonlinear optical properties of ionic organic crystals” [J. Chem. Phys. 141, 104109 (2014)]

Cation 0th −7.05 −2.44 0.45 7.48 −1.87 −0.05 0.32 1.90 3rd −11.82 −3.80 1.07 12.46 −1.76 −0.04 0.33 1.79 Anion 0th −11.34 0.90 0.85 11.41 −4.35 0.18 0.43 4.37 3rd −14.72 1.09 0.85 14.80 −4.28 0.21 0.40 4.31

Emergence of Nonlinear Optical Activity by Incorporation of a Linker Carrying the p-Nitroaniline Motif in MIL-53 Frameworks

p-Nitroaniline presents the typical motif of a second-order nonlinear optically (NLO) active molecule. However, because of its crystallization in an antiparallel and hence centrosymmetric structure, the NLO activity is lost. In this contribution, the p-nitroaniline motif was built successfully into the MIL-53 metal–organic framework. More precisely, MIL-53 was synthesized with 2-amino-5-nitroterephthalate as organic linker, with Al3+, Ga3+, or In3+ as inorganic cation. The Al and Ga structures are polar, as confirmed by second-harmonic generation microscopy, yielding stable NLO materials. Indeed, they contain a 22–36% surplus of the dipolar 2-amino-5-nitro-terephthalate oriented in a parallel fashion. The indium compound was shown to be less crystalline and centrosymmetric. Ab initio modeling of the second-order NLO response shows that the Al and Ga materials show a response comparable to typical inorganic commercial NLO materials such as KDP. As a hybrid material, capable of low-temperature synthesis and processing and the ultrafast NLO responses associated with organic materials, this material can potentially provide an interesting venue for applications with respect to traditional inorganic NLO materials.

Crystal engineering, optical properties and electron density distribution of polar multicomponent materials containing sulfanilamide

Two polar multicomponent materials: sulfanilamide sulfamic acid salt (P21) and sulfanilamide [(4-sulfamoylphenyl)carbamoyl]formic acid salt (Pc) were designed using crystal engineering techniques. A full analysis of the interactions present in both materials was performed by means of topological descriptors of the theoretical electron density. The detailed characterization of S–X (X = O, N, C) bonds by valence shell charge concentration and source function analysis revealed the strongly polarized, almost ‘ionic’ character of S–O interactions. The obtained results show that mutual assembly of crystal building blocks and their packing in both crystal structures is influenced by N–H⋯O hydrogen bonds with an intermediate character between closed and shared shell interactions. Their presence can be associated with hydrogen atom transfer leading to salt formation. Linear (birefringence) and nonlinear optical properties (second harmonic generation) were examined for both materials. The theoretical calculations of χ(2) tensor components and the dispersion of refractive indices revealed that both materials are phase-matchable with second harmonic generation efficiency comparable with commonly used KDP (KH2PO4). One of the materials shows large birefringence (ca. 0.3), which is confirmed by the observation of interference colours strongly dependent upon the sample thickness.

Co‐Crystals of 2‐Amino‐5‐Nitropyridine Barbital with Extreme Birefringence and Large Second Harmonic Generation Effect

Technological innovation enforces a revolutionized approach towards materials chemistry. In this paper a new methodology towards crystal engineering of polar materials for possible applications in linear or non-linear optics (NLO), as well as ferroelectric, pyroelectric or piezoelectric crystals is presented. The necessity to fulfil several criteria concerning symmetry, electron properties of the building blocks, and also mechanical and optical stability was achieved by fusion of a pharmaceutical molecule and an NLO-phore. Co-crystals of 2-amino-5-nitropyridine barbital, presented in this manuscript, show cutting-edge optical performance. Large second harmonic generation (SHG) efficiency (40 times better than potassium dihydrogen phosphate, KDP), extreme birefringence (2.7 times higher than for calcite), simplicity in preparation, and optical and mechanical stability of the product proves that in fact a new generation of smart materials was obtained.

From molecules to materials, efficient crystal engineering of polar systems

Technological progress enforces improved materials performance, therefore controlling synthesis of new systems requires moving from trial-and-error methods to comprehensive solutions. Understanding of molecular self-assembly requires assessment of all features which characterize building blocks and contribute to the unique physical properties of a crystal. Novel polar materials designed for applications in linear or non-linear optics or as ferroelectrics have to fulfil several criteria concerning symmetry (necessary condition), electron properties of the building blocks as well as mechanical and optical stability. For this purpose the chosen components must possess high molecular polarizability/hyperpolarizability and what is more promote the formation of three dimensional noncentrosymmetric crystal structure. Here we present our approach for efficient crystal engineering of multicomponent systems built of Active Pharmaceutical Ingredients (API) ensuring synthon formation flexibility and combined with push-pull molecules providing required electronic properties of a material [1]. The goal is to create a new polar material from the known starting components to ensure desired bulk properties of a crystal. In our research we combine quantitative and in silico crystal engineering techniques together with prediction and measurements of optical properties. Noncovalent Interaction Analysis (NCI) [2], Hirshfeld surfaces and fingerprint plots [3], topology of electron density (ED) are a set of tools for the characterization of interand intramolecular interactions in the context of understanding structure-property relationship. This approach enables reliable assessment of selected co-formers as well as the obtained materials.

Charge-density studies of multicomponent crystals containing API sulfanilamide

Fast development of technology requires constant introduction of more and better solutions in material science. Efficient nonlinear optical smart materials have to fulfil several conditions including lack of inversion centre, high hyperpolarizabilities of the building blocks and mechanical stability [1]. Accomplishment of all of these nontrivial requirements is possible with multicomponent crystals. At least one of the building blocks increases electronic properties of material, while mutual assembly of building blocks provides non-centrosymmetricity. Promising components could be Active Pharmaceutical Ingredients (APIs) which possess synthon formation flexibility, are nontoxic and often cheap [2]. In our work sulphanilamide, an antibacterial drug, which is also a NLO chromophore was used as a starting point. The second component was chosen to utilize favourable donor\acceptors sites of sulphanilamide and to ensure polar mutual orientation of molecules. Crystal engineering techniques were combined with charge density studies in order to design materials with more efficient properties. Understanding of the intermolecular interactions and mutual assembly of building blocks in 3D structure is crucial for improving crystals performance. The properties of obtained materials were also predicted by theoretical calculations.