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Crystal Structures and Thermodynamic Properties of Polymorphs and Hydrates of Selected 2‑Pyridinecarboxaldehyde Hydrazones Liliana Mazur,*,† Katarzyna N. Jarzembska,‡ Radosław Kamiński,‡ Anna A. Hoser,‡,§ Anders Ø. Madsen,§ Edyta Pindelska,∥ and Monika Zielińska-Pisklak∥ †

Department of Chemistry, Maria Curie-Skłodowska University, Maria Curie-Skłodowska Square 2, 20-031 Lublin, Poland Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, Ż wirki i Wigury 101, 02-089 Warsaw, Poland § Department of Chemistry, University of Copenhagen, Universitetparken 5, 2100 Copenhagen, Denmark ∥ Department of Pharmacy, Medical University of Warsaw, Banacha 1, 02-097 Warsaw, Poland ‡

S Supporting Information *

ABSTRACT: Synthesis, crystal structure, and thermal behavior studies of different solid-state forms of two new 2pyridinecarboxaldehyde N-acylhydrazones are reported together with the corresponding computational analyses. Both compounds exist in two anhydrous polymorphic forms and crystallize also as hydrates. All of the studied crystals were obtained via solvent evaporation from solutions. Structural features were determined using single-crystal XRD (employing the transferred aspherical atom model, TAAM) supported by solid-state NMR. The relative stability of different crystal forms was examined experimentally using the TGA-DSC methods and supplemented with extended lattice and interaction energy calculations and crystal entropy estimation. The results confirmed the prevalent role of strong hydrogen bonds of N−H···O and N−H···N type in stabilization of anhydrous crystals. In the case of hydrates, water molecules incorporated into the crystal network are involved in the most efficient hydrogen bonds contributing significantly to the crystal cohesive energy. The TG-DSC studies showed that the denser polymorphic forms are more thermodynamically stable at higher temperatures, and excluded any thermal events before the melting point in the case of anhydrous crystals. Energy and entropy calculations were confronted with the experimental thermodynamic results. pair of the azine N1 atom. Furthermore, the presence of an additional CO donor site induces an extended π-electron delocalization along the whole C(O)−NH−NC fragment. Consequently, the acylhydrazone unit is almost planar as long as there is no steric hindrance between the substituents around the CN bond.6,9−11 The carbon and nitrogen atoms forming the CN bond constitute the most reactive centers of the acylhydrazone moiety. Due to high chemical reactivity, NAHs are widely used in chemical synthesis, mainly as precursors and intermediates of different heterocycles, 2,6 but also as intermediates in the synthesis of aza compounds.10,11 Recently, scientific attention has been focused on the application of Nacylhydrazones as templates for metal catalysts.9−11 Their role in analytical chemistry is also significant, as they are used for detection of carbonyl compounds and transition-metal ions.12,13 However, the most extensive studies nowadays are devoted to their biological activity. N-Acylhydrazones constitute a

1. INTRODUCTION N-Acylhydrazones (NAHs) constitute a versatile class of imine compounds with the general formula R−C(O)−NH−N C−R′ (Scheme 1). As is the case for many other azomethine Scheme 1. General Synthetic Route of the Studied Hydrazones (R = 3-OCH3-C6H4 (1), CH2-C6H5 (2)), and a Numbering Scheme

derivatives, they can be obtained in a reaction of acid hydrazides with a carbonyl compound.1−5 The resulting double CN bond contributes to the formation of geometrical E/Z isomers. In addition, N-acylhydrazones can form conformational isomers due to a partly hindered rotation around the azine N−N and/or amide C−N bonds.6−8 The imine πelectrons in hydrazones are conjugated with the lone electron © 2016 American Chemical Society

Received: November 25, 2015 Revised: March 31, 2016 Published: April 14, 2016 3101

DOI: 10.1021/acs.cgd.5b01673 Cryst. Growth Des. 2016, 16, 3101−3112

Crystal Growth & Design

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Table 1. Selected Structural Data (for more details see the Supporting Information) Crystal structure

1a

1b

1·H2O

2a

2b

2·H2O

Chemical formula M /g·mol−1 Crystal system T/K Space group a/Å b/Å c/Å α/deg β/deg γ/deg V/Å3 Z

C14H13N3O2 255.26 orthorhombic 100 Pbca 12.015(2) 8.248(1) 25.660(3) 90 90 90 2543.0(6) 8

C14H13N3O2 255.26 monoclinic 100 P21/c 8.9565(4) 14.7645(6) 19.5706(9) 90 99.770(4) 90 2550.4(2) 8

C14H15N3O3 273.28 monoclinic 100 P21 6.5870(3) 28.476(1) 7.0439(3) 90 101.094(4) 90 1296.5(1) 4

C14H13N3O 239.26 monoclinic 90 P21/c 12.3551(4) 9.4084(2) 11.0578(4) 90 107.605(4) 90 1225.18(7) 4

C14H13N3O 239.26 monoclinic 90 P21/c 8.9209(4) 16.7481(6) 8.5435(3) 90 103.154(4) 90 1242.98(8) 4

C14H15N3O2 257.28 triclinic 100 P1̅ 6.4007(5) 8.6422(7) 11.7988(5) 94.181(5) 90.804(5) 96.049(7) 647.15(8) 2

head using Paratone N oil, and cooled down to 90 or 100 K. Data collection strategies were monitored with the CRYSALIS PRO29 program suite. Unit cell parameter determination, raw diffraction image integration, Lorentz and polarization corrections, oblique incidence effects, multiscan absorption corrections, and frame-toframe scaling were performed with the diffractometer software. Merging of reflections was carried out with the SORTAV program.30,31 All structures were solved by direct methods using the SHELXS program,32 and refined with the SHELXL program32 within the IAM (independent atom model) approximation. In all the cases, the positions of hydrogen atoms and orientations of methyl groups were determined from Fourier residual maps. Subsequently, transferred aspherical atom model (TAAM)33−39 refinements were performed in the MOPRO package40 with the aid of the new version of the University at Buffalo Databank (UBDB)41 and the LSDB program,36,41,42 based on the Hansen-Coppens multipole model.43 During TAAM refinements, all electron density parameters are kept fixed at the databank values, whereas the scale factor, atomic positions, and atomic displacement parameters (ADPs) are iteratively varied. Atom types specific for hydrazone molecules, and not present in the original UBDB version, were taken from our previous work.28 The crystallographic data are given in Table 1, whereas the final data collection parameters and refinement statistics for all compounds are summarized in Table 2S (Supporting Information). The CIF files for each refinement are available from the Cambridge Crystallographic Data Centre (CCDC)44 (deposition numbers CCDC 1406086− 1406091). 2.3. NMR studies. 13C and 15N spectra were recorded at room temperature on a Bruker Avance 400 WB spectrometer at 9.4 T, operating at 100.61 and 40.50 MHz resonance frequencies, respectively. A Bruker 4.0 mm HX double-resonance magic-angle spinning (MAS) probe was applied. The 13C and 15N experiments were performed using cross-polarization (CP), high power decoupling, and MAS with 4 mm zirconia rotors driven by dry air. The MAS rates were 7.5 kHz and in a range of 3.5−5.0 kHz for 13C and 15N, correspondingly. All NMR spectra were processed, and overlapped signals were deconvoluted with the ACD/SpecMenager NMR program.45 In order to verify the signal assignment, GIPAW calculations of shielding constants based on X-ray structures of NAHs were performed using the Cambridge Serial Total Energy Package (CASTEP) program46 implemented in the Materials Studio 6.1 software.47 More details about NMR computations48,49 can be found in the Supporting Information. 2.4. Thermal analysis. The thermal stability of the studied hydrazones was examined using a Setsys 16/18 (Setaram) thermal analyzer, recording the TG/DTG/DSC curves. Crystals obtained from the crystallization batches were air-dried before being subjected to DSC or TGA measurements. The samples (4−7 mg) were heated in a ceramic crucible between 30 and 900 °C in a flowing air atmosphere with a heating rate of 10 K·min−1. Solvent loss from the crystals was characterized by TG. The temperature of the dehydration processes as

promising class of compounds for drug development. Some of them exhibit antibacterial and antitubercular,14−20 antitumor,21−23 analgesic, and anti-inflammatory24,25 activity. Several acylhydrazone derivatives have already been approved as pharmaceuticals (e.g. Nifuroxazide, Iproniazide, Isocarboxazide, and Desferrioxamine), and some others are under clinical trials.26,27 Inspired by their chemical and medical potential, we have recently synthesized a series of 2-pyridinecarboxaldehyde Nacylhydrazonespossible cytostatic agents. Consequently, we have previously characterized the structural properties of some N-acyl- and N-aroylhydrazones,28 whereas the results of biological studies will be published elsewhere. Here we address the polymorphism and hydrates of two other derivatives (Scheme 1). The three main points discussed in this study are (i) the interaction preferences, (ii) the influence of the incorporation of H2O on intermolecular−interaction patterns and crystal packing features, and (iii) the relative stability of different crystal forms of the studied compounds. To achieve these goals, experimental and theoretical methods have been combined, including single-crystal X-ray diffraction, solid-state nuclear magnetic resonance (SS-NMR), and TGA-DSC (simultaneous thermogravimetric analysis and differential scanning calorimetry), as well as DFT (density functional theory) energy calculations and crystal entropy evaluation.

2. EXPERIMENTAL SECTION 2.1. Materials and methods. All chemicals and solvents were purchased from commercial sources (Sigma-Aldrich Co., USA, and Polish Chemical Reagents, Poland) and used without further purification. Infrared spectra (4000−600 cm−1) were recorded on a Nicolet 6700 FT-IR spectrophotometer (in the ATR mode, ZnSe crystal). Elemental analyses were performed on a CHN PerkinElmer 2400 analyzer. The hydrazones of interest were synthesized by condensation of 2pyridine-carboxaldehyde with the corresponding acid hydrazides in methanol solution (Scheme 1) following the literature procedure.1−5,28 Single crystals suitable for X-ray diffraction studies were grown from the mother liquor by slow evaporation at room temperature or recrystallized from common organic solvents (see further discussion). The physicochemical and spectral characteristics of all studied forms are given in Table 1S (Supporting Information). 2.2. Crystal structure determination. Single-crystal X-ray diffraction experiments were performed on an Agilent Technologies Xcalibur CCD diffractometer equipped with a Mo sealed X-ray tube (Mo Kα radiation, λ = 0.71073 Å), a graphite monochromator, and an Oxford Cryosystems Cobra Plus nitrogen gas-flow device. In all the cases, single crystals of suitable sizes were mounted on a goniometer 3102



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well as temperatures and enthalpies of fusion (Table 1S, Supporting Information) were established on the basis of the DSC curves. 2.5. Computational studies. All energy computations within the CRYSTAL program package (CRYSTAL09 version) were performed at the DFT(B3LYP) level of theory50−52 using 6-31G**53 molecular allelectron basis set. Both Grimme dispersion correction54−56 and correction for basis set superposition error57 (BSSE) were applied. The TAAM refined crystal geometries were used for the purpose of the CRYSTAL computations. The cohesive energy (Ecoh) was calculated following the procedure described in the literature:33,58,59Ecoh = (Ebulk/Z) − Emol, where Ebulk is the total energy of a system (calculated per unit cell) and Emol is the energy of an isolated molecule extracted from the bulk (with the same geometry as in the crystal phase). Z stands for the number of molecules in the unit cell. CRYSTAL package was additionally applied for the dimer interaction energy estimation at the B3LYP/6-31G** level of theory. The supermolecular approach was applied with both Grimme dispersion and BSSE corrections. The methodology is essentially the same as used in our previous paper.28 All input files were prepared using the CLUSTERGEN program.60 2.6. Crystal entropy estimation. The vibrational entropy at a given temperature, associated with low-frequency modes, was calculated from the frequencies obtained after the translationlibration-screw (TLS) analysis61−64 (TLS fit was performed with the THMA program,62 by applying the harmonic oscillator model approximation, as described by Madsen and Larsen.65) The highfrequency vibrational modes were calculated using the CRYSTAL code. The geometry optimizations and frequency calculations were carried out at the DFT(B3LYP)/6-31G** level of theory.66,67 As a result of CRYSTAL calculations we obtained both the “internal” and “external” vibrational entropy contributions based on the normal-mode frequencies at the Γ point, which consequently, do not include the important contribution from the acoustic phonons. However, a combination of the results of theoretical calculations and the TLS analysis provides a more realistic estimation of the total entropy value for the considered system. Therefore, we replace the CRYSTALcalculated low-frequency modes with those obtained from the segmented TLS approach. A reasonable cutoff limit between the low- and high-frequency modes was found applying the rule of Willis and Pryor,68 where the first 6×Z “external” modes are rejected (this approximation works best for rigid molecular crystals).

Table 2. Crystallization Conditions and Resulting Crystal Forms of 1 and 2a Solvent used

Compd 1

Compd 2

water MeOH MeOH + H2O MeOH + morpholine EtOH 1-propanol 2-propanol 1-butanol 1-pentanol acetone MeCN ethyl acetate 1,4-dioxane THF DMF DMSO chloroform chlorobenzene

1a 1a 1a + 1·H2O 1a 1a 1a 1b 1b 1a 1a 1a 1a 1a 1a 1a 1a 1a 1a

2b 2a 2b 2·H2O + 2b 2b + 2a 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b

a

Abbreviations: MeOH, methanol; EtOH, ethanol; MeCN, acetonitrile; THF, tetrahydrofuran; DMF, dimethylformamide; DMSO, dimethyl sulfoxide.

containing organic solvent molecules, even the most polar ones, were observed. 3.2. Molecular structures. The relevant geometric parameters for all structures are given in Table 3S (Supporting Information). Molecular plots with the atom-labeling schemes are presented in Figure 1. In general, compounds 1 and 2 crystallize in common centrosymmetric space groups (P1̅, P21/ c, and Pbca) with one (1a, 2a, 2b, and 2·H2O) or two (1b, 1· H2O) hydrazone molecules in the asymmetric unit (ASU). The only exception here is the 3-methoxyphenyl derivative, which forms the 1·H2O chiral crystal structure (P21 space group) with two isomers of the organic component in the asymmetric unit. As indicated by the X-ray data, in all the studied crystals the hydrazone molecules appear in their keto tautomeric forms with the trans configuration around the C2N2 double bond of the hydrazone bridge and a cis arrangement of the hydrazide C1(O1)−N1−N2 function (Figure 1). The central C3− C2−N2−N1−C1−C8 spacer unit is effectively planar with the all-trans extended-chain conformation, as evidenced by the appropriate torsion angles being close to 180° (Table 3S, Supporting Information). Another common conformational feature is the trans arrangement of the pyridine N3 with respect to the imine N2 atom, as defined by the N2−C2−C3−N3 torsion angles, which deviate by no more than ±4° from 180°. This is in agreement with our observations made for some other N-aroyl-hydrazones.28 There are also no significant differences in the bond lengths and angles (Table 3S, Supporting Information) within the central functional spacer. In general, all interatomic distances are within typical ranges for this class of compounds,1−5,69,70 and the single and double bonds are easily distinguishable. The most visible conformational dissimilarities between molecules concern the relative arrangement of their terminal units. The differences in the overall geometry are mostly due to rotation around the C1−C8 bond. In the orthorhombic 1a form, there is only one molecule in the asymmetric unit with the 3-methoxy substituent at the same edge as the C1O1

3. RESULTS AND DISCUSSION 3.1. Crystallization. Depending on the crystallization conditions, both compounds can crystallize as their unsolvated forms or hydrates (Table 2). Similar observations were previously made for some other closely related 2-pyridinecarboxaldehyde hydrazones.28 The studied hydrazones form welldefined single crystals, namely 1a and 2b, via solvent evaporation from the stock solution. The other polymorphic modification of 1, referred to as 1b, can be crystallized from 2propanol or 1-butanol, whereas a new form of 2 (polymorph 2a) was grown from pure methanol. Slow evaporation of 2 from ethanol (98.6%) resulted in concomitant crystals with different morphologies identified as a mixture of 2a and 2b. In turn, the hydrated forms of 1 and 2 were harvested from methanol−water (1:1 v/v) (1·H2O) or methanol−morpholine (40:1 v/v) mixtures (2·H2O). On complete evaporation of the solvent, the resulting samples were identified as a mixture of 1a and 1·H2O (compound 1) or 2b and 2·H2O (compound 2). All crystals remain stable and are characterized by high quality diffraction data even after storage for a few months, except for 2·H2O hydrate, crystals of which decompose rapidly under ambient conditions. Crystallization of compounds 1 and 2 from other common organic solvents leads most often to forms 1a and 2b, respectively (Table 2). Interestingly, no crystal structures 3103



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Figure 1. Labeling of atoms and estimation of their thermal motion parameters as ADPs (50% probability level) after TAAM refinements.

hydrogen bonds of the N−H···O and/or N−H···N type play a dominant role. In all of them, the amide NH group acts as a donor, whereas the amide O1 or hydrazone N2-atoms act as hydrogen bond acceptors (Table 4S, Supporting Information). The anhydrous crystals are characterized by comparable cohesive energy values around −160 kJ·mol−1 per hydrazone molecule (Table 3). In the case of 1, the two polymorphic

moiety. Whereas in the monoclinic 1b form two symmetry independent molecules are observed, both with the trans arrangement of − OCH3 with respect to the carbonyl C1O1 group. The two molecules in 1b differ from each other mostly in the relative orientation of the phenyl rings with respect to the remaining part of the molecule, as evidenced by the torsion angles O1−C1−C8−C9 and O3−C15−C22−C23 being 179.7(2)° and 156.0(1)°. Still another difference is in the orientation of the 3-methoxy substituent (Figure 1), which is cis (1bA) and trans (1bB) with respect to the ortho C9/C23 atom of the phenyl ring. In the hydrate 1·H 2O, each of the two symmetry independent hydrazone molecules are characterized by a similar geometry of the central acylhydrazone unit and the syn arrangement of the 3-methoxy substituent. The substantial conformational difference is in the geometry of the −OCH3 group, which is in the plane of the phenyl ring in molecule B and is rotated by 26.6° (Table 3S, Supporting Information) from the respective plane in molecule A. In the case of compound 2, the higher molecular flexibility (due to the presence of an additional methyl spacer) results in the conformational polymorphs 2a and 2b, which differ in the relative orientation of the phenyl ring with respect to the remaining molecular fragment. The conformational changes are caused by the simultaneous rotations around the C1−C8 and C8−C9 single bonds (Table 3S, Supporting Information). The molecules of 2 adopt a bent conformation in the solid state. The phenyl ring and amide group are almost perpendicular, as indicated by the dihedral angles between their best planes equal to 71.96(1)°, 74.39(1)°, and 70.73(1)° in 2a, 2b, and 2·H2O, respectively. 3.3. Supramolecular structures and energetic features. In general, among the intermolecular interactions involved in stabilization of all studied crystals, the strong

Table 3. Cohesive Energy Values Calculated for the Studied Crystals in Their Hydrous and Anhydrous Formsa Crystal structure

ASU content

Ecoh/kJ·mol−1

−1 Eanh coh/kJ·mol

1a 1b 1·H2O 2a 2b 2·H2O

1H 2H 2H + 2W 1H 1H 1H + 1W

−160.7 −319.4b/−158.7c −443.8b/−221.9c −159.2 −164.8 −224.3

− − −293.2b/−119.6c − − −115.9

ASU content abbreviations: H − hydrazone molecule, W − water molecule; Ecoh − cohesive energy, Eanh coh − cohesive energy of an imaginary structure with removed water. bValue given per ASU. c Averaged value given per a half of ASU (for better comparison with the other structures). a

structures differ only by 2 kJ·mol−1 on average, which suggests that the formation of a particular crystal type is most probably governed by other factors, such as kinetics, entropy, etc. The energetic difference is slightly more pronounced (5 kJ·mol−1 per hydrazone moiety) when one compares the total energies of the asymmetric unit in both polymorphs. The relatively most energetically stable anhydrous crystal is 2b. It is also the most commonly observed polymorphic structure in the case of compound 2 (Table 2). 3104



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Figure 2. Intermolecular interactions (represented as thin lines) in crystal 1a: (a) hydrogen-bonded molecular chains with a R21(6) ring motif; (b) molecular ribbons via weak C−H···N and C−H···O interactions; (c) crystal packing viewed along the X axis.

Scheme 2. Supramolecular Synthons in the Studied Crystal Structures

Compared to the previously reported crystal structures of the 2-pyridinecarboxaldehyde N-acetyl- or N-benzoyl hydrazones,28 the intermolecular interaction patterns in the currently studied crystals are much more complex. Chemical modification of compounds through replacement of the methyl or phenyl group via the 3-methoxyphenyl or phenyl acetyl unit not only enlarges the scope of possible intermolecular interactions but also makes the compound prone to polymorphic modifications. This is also reflected in substantially more favorable cohesive energy values of both hydrous and anhydrous crystal forms of the currently studied compounds when related to the analogous previously analyzed hydrazone structures. 3.3.1. 2-Pyridinecarboxaldehyde (3-methoxybenzoyl)hydrazone. The crystal structure of orthorhombic form 1a can be treated as constructed from two simple 1D substructures, one of them dominated by strong N−H···O hydrogen bonds and the other one based solely on weak C− H···N and C−H···O interactions. In the first prominent motif the molecules are linked by three-center N1−H1N/C2−H2··· O1 (Figure 2a; Table 3S, Supporting Information) hydrogen bonds, resulting in [010] molecular chains via the R12(6) ring motif. The total interaction energy of the resulting hydrazoneamide homosynthon I (Scheme 2) is −64.1 kJ·mol−1. The

In the hydrates, 1·H2O and 2·H2O, the primary acceptors are water molecules. Incorporation of water into the crystal modifies the hydrogen-bonding patterns, which further impose quite different supramolecular arrangements. Water molecules saturate effectively the hydrogen bond acceptor and donor centers, especially the N3/N6 atoms, which are involved only in some secondary interatomic contacts in the anhydrous crystal forms. Consequently, water built-in the structure results in significantly more advantageous crystal cohesive energies, which is in agreement with our previous findings.28 The energy gain amounts to about 105 kJ·mol−1 when compared to the structures with excluded water moieties (Table 3), or to about 62 kJ·mol−1 per asymmetric unit confronting the hydrated and anhydrous forms. Such numbers reflect additional hydrogen bonds formed when water is present in the crystal networks. Each water molecule is involved in three hydrogen bonds, which results in at least two additional relatively strong interactions with respect to the anhydrous forms. Again the cohesive energy values are comparable for 1·H2O and 2·H2O. The hydrated crystals, however, are much less commonly formed when compared to the corresponding solvent-free forms. 3105



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Figure 3. (a) Hydrogen-bonding in crystal 1b, resulting in [010] molecular chains; (b) weak lateral intermolecular interactions; (c) crystal packing viewed along the X axis.

Figure 4. Features of the 1·H2O crystal structure: (a) hydrogen-bonding patterns involving molecules A (light blue) and B (dark blue); (b) two types of hydrogen-bonded chains propagating along the X axis (view along the Z axis); (c) weak C−H···O/π interactions and π···π stacking contacts; (d) crystal packing (view along the X axis).

bonding involving amide functions plays the most important role. Each of the two amide O1, O3 atoms from two different molecules 1bA and 1bB simultaneously forms three hydrogen bonds, with amide N1/N4, hydrazone C2/C16, and phenyl C9/C23 atoms (Table 4S, Supporting Information) as Hdonors, respectively. Consequently, two different types of hydrogen-bonding ring motifs are formed: R12(6) (R1/R3) and R12(7) (R2/R4) (Figure 3a). In the former case, amide N1 and phenyl C9 atoms (molecule 1bA) are additionally involved in hydrogen-bonding to hydrazone N5 or amide O3 atoms (from molecule 1bB), respectively, yielding the ring motifs R5 and R6 (Figure 3a). The respective dimeric motifs are stabilized by the energies of −63.4 kJ·mol−1 and of −49.6 kJ·mol−1 (Table 4S, Supporting Information). In analogy to form 1a, the relative

second type of 1D architectures are planar molecular ribbons (Figure 2b) parallel to the [100] direction, via weak Carom−H··· Nhydr and Carom−H···Oamide hydrogen bonds (Table 4S, Supporting Information). The ribbons stack along the b axis in an antiparallel and offset manner, giving layers enforced via C−H···π and π···π contacts (Figures 2a and c). Auxiliary Carom−H···πarom interactions (Figure 2c) between the adjacent layers complete the 3D packing. The hydrogen-bonded chain with hydrazone-amide homosynthons I (Scheme 2) is also observed in monoclinic form 1b. However, this time the aggregates are formed by alternately arranged, symmetry independent molecules 1bA and 1bB (Figure 3a). As in 1a, among the intermolecular interactions involved in stabilization of the crystal structure of 1b, hydrogen 3106



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Figure 5. (a) Intermolecular interactions (thin lines) in the crystal structure of 2a; (b) weak C−H···N interactions; (c) crystal packing (view along the Y axis).

Figure 6. (a) Intermolecular interactions in the 2b crystal creating [001] chains; (b) (010) molecular layer stabilized through weak C−H···N and C−H···π contacts; (c) part of the crystal structure in view along the Z axis.

3.3.2. 2-Pyridinecarboxaldehyde (phenylacetic)hydrazone. The two polymorphic forms of phenylacetic acid hydrazone (2) crystallize in the same space group P21/c with Z′ = 1. Nevertheless, there are visible differences in their crystal packing and hydrogen-bonding features. In general, their crystal structures can be described as 2D hydrogen-bonding networks, wherein the amide−amide N−H···O interactions play a dominant role. In 2a, the adjacent 21 screw axis related molecules are linked into helical chains by a combination of strong N1−H1N···O1 (homosynthon I) and weak C8−H8a···O1 hydrogen bonds, which together create R12(6) ring motifs (Figure 5a). The total stabilization energy of the synthon, being about −60 kJ·mol−1, is comparable to those calculated for similar motifs found in 1a and 1b structures. The antiparallel, inversion-related chains interact with each other by weak C−H···N contacts involving benzyl C8, C14, hydrazone N2, and pyridine N3 atoms (Table 4S, Figures 5b and c). This results in a 2D (100) layered architecture, in which molecules are arranged in such a way that their hydrophilic parts are located inside and the hydrophobic ones outside each layer. The interlayer stabilization of the structure is provided solely via C−H···π contacts involving aromatic rings (Figures 5b and c). The most important dissimilarities between crystal structures 2a and 2b are in the relative orientation of molecules creating the main supramolecular motif. In polymorph 2b, the hydrogen-bonded chains are created by c-glide-plane-related molecules being almost perpendicular one to another. The dihedral angle between the best-planes of their amide groups is equal to 56.1°, whereas the corresponding angle in 2a amounts

orientation of molecules within each chain enables formation of lateral C−H···π interactions (Figure 3a) between two aryl rings from the neighboring, 21 screw axis related molecules 1bB. The adjacent antiparallel chains are assembled into the 3D network through weak C−H···N and C−H···O hydrogen bonds (Table 4S, Figures 3b and c). In spite of the differences in molecular composition and internal symmetry of the crystals, the supramolecular pattern in 1·H2O is quite similar to that observed in the previously reported 28 2-pyridinecarboxaldehyde benzoyl- and (2aminobenzoyl)hydrazone hydrates. However, the separation of conformationally different host molecules (A and B) in the considered crystal is clearly visible. Within the selected asymmetric unit, two independent (host and guest) molecular components are linked by strong Namide−H···Owater hydrogen bonds and weak C−H···Owater contacts (Table 4S, Figures 4a and b). These bimolecular units are further connected via strong bifurcated Owater−H···(O1,N2)hydrazide hydrogen bonds characterized by the energy of −27.9 (water···A) and −35.1 kJ· mol−1 (water···B) into the chains of molecules (Figures 4b and d) bonded by the hydrazone-water-amide heterosynthon II (Scheme 2). The symmetry independent parallel chains are connected by cyclic hydrazone-water-pyridine heterosynthon III (Scheme 2) via strong O1w−H2w···O3, O2w−H4w···N3 and weak C28−H28···O1 (Table 4S, Figure 4a) hydrogen bonds. The double chains stack along the Z axis, resulting in (010) molecular layers. The inter- and intralayer stabilization is provided by numerous weak C−H···O/π and π···π contacts (Figures 4c and d). 3107



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molecules, resembles that in crystal 1·H2O. The host and guest units are linked by hydrazone-water-amide heterosynthon II (Scheme 2, Figure 7a), stabilized by ca. − 57 kJ·mol−1, into [100] supramolecular chains. Nevertheless, the bent conformation of the host molecule enforces significant changes in the relative orientation of the adjacent chains. The inversionrelated 1D motifs are interconnected by Owater−H···Npyridyl hydrogen bonds (heterosynthon III) into molecular columns (Figure 7c), which are further linked via centrosymmetric Calkyl−H···Oamide hydrogen bonds into (010) layers. The relative orientation of the adjacent layers enables formation of phenyl−water and phenyl−hydrazone C−H···O/N contacts which complete the 3D packing (Figures 7b and c). 3.4. Solid-state NMR studies. Solid-state NMR (SSNMR) spectroscopy combined with quantum mechanical computations of NMR shielding was used as a complementary technique to X-ray crystallography, enabling investigations of both inter- and intramolecular interactions in polycrystalline samples of the studied N-acylhydrazones. Figure 8 shows the 13 C CP/MAS NMR spectra acquired for the anhydrous polymorphs 1a, 1b and 2a, 2b as well as, for monohydrate, 1·H2O. Tables 5S and 6S in the Supporting Information present the 13C and 15N NMR chemical shifts observed for these compounds. The discussion of the SS-NMR data is given in the Supporting Information file. 3.5. TG-DSC analysis. The thermal stability of the studied hydrazones and their hydrates, except for 2·H2O (due to the fast desolvation process at room temperature), was assessed by the simultaneous DSC and TG analysis. The melting-point values (onset points) for all forms and enthalpies of fusion for the unsolvated hydrazones (Table 1S, Supporting Information) were determined from the DSC curves. The DSC analysis of two polymorphs of 1 and 2 (Figure 9, blue and red lines) indicated that the denser forms 1a and 2a (Tm = 139 and 167 °C; ΔHf = 21.5 kJ·mol−1 and 31.8 kJ·mol−1, respectively) are more stable than the corresponding forms 1b and 2b (Tm = 127 °C and 156 °C; ΔHf = 19.8 kJ·mol−1 and 26.4 kJ·mol−1). The TGA of 1a, 1b, 2a, and 2b showed a weight loss of less than 0.5% prior to the melting-point, confirming that these forms are indeed anhydrous. At the same time, no peaks on the DSC curves before the final melting were observed, excluding any

to 9.0°. Within each chain, the molecules are held together by short, almost linear N1−H1N···O1 hydrogen bonds (homosynthon I) and the assembly is reinforced by the weak lateral C8−H8b···N2, C14−H14···O1 contacts (Figures 6a and b), resulting in a total stabilization energy of −64.8 kJ·mol−1. In turn, the layered aggregation is based on an extensive net of weak C−H···O/N/π − type contacts (Figure 6a and Table 4S). As for 2a, the interlayer stabilization is accomplished exclusively through weak C−H···π and π···π interactions (Figures 6b and c). The water molecules incorporated into the crystal 2·H2O play the role of “molecular glue”, which links adjacent host units into a complex supramolecular architecture. The hydrogen-bonding pattern (Table 4S, Figure 7a), involving water

Figure 7. (a) Intermolecular interactions involving water molecules in the crystal of 2·H2O; (b) weak hydrogen bonds; (c) crystal packing (view along the X axis).

Figure 8. 13C CP/MAS NMR spectra of (a) 1a,1b and 1·H2O, and (b) 2a and 2b acquired with the contact time of 4 ms. The 13C spinning side bands are marked with asterisks. 3108



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Figure 9. DSC (solid lines) and TGA (dashed lines) curves for: (a) 1a (blue), 1b (red), and 1·H2O (green), and (b) 2a (blue) and 2b (red). Colored numbers indicate melting-point temperatures (onset values) (see Supporting Information).

thermal events before melting (for TGA-DSC experiments on 2b with different heating rates (5 K·min−1 and 1 K·min−1) see Figure 1S, Supporting Information). This has largely been confirmed by variable temperature XRPD (Figure 2S, Supporting Information). The thermal dehydration of 1·H2O is characterized by a single broad peak on the DSC curve (Figure 9a, green line), ranging from 55 to 123 °C, with the maximum at 79 °C and the total weight loss of about 6.66%. Then, the dehydrated product is stable up to the melting point of the crystals Tm (= 143 °C). The weight loss calculated from the crystal structure provides the value of 6.59%, confirming that dehydration proceeds with the complete removal of the water from the crystals. 3.6. Entropy and relative stability of polymorphs. Generally, when the relative stability of polymorphs is discussed, most calculations are focused on the cohesive (or lattice) energy, and no effort is put forth to take the entropy into account. Such an approach may lead to incorrect order of stability of crystal structures, since the latter is determined by the minimum of the Gibbs free energy (at a given temperature). This is a natural consequence of the fact that the stability of polymorphic structures depends on both the enthalpy (energy of a “frozen” structure) and the term which arises from the thermal vibrations of molecules and the whole crystal lattice. According to the recent computational study of Nyman and Day71 (carried out for a large group of polymorphic systems; >500 systems), in the case of about 10% of polymorphs, a small difference in the entropy contribution to the free energy reranks the stability of polymorphs at room temperature. It has been shown that the multitemperature X-ray diffraction data may yield useful thermodynamic information, when a rigid-body or semirigid-body model approach is applied to ADPs.72−75 The recent results reported by Madsen and Larsen65,76 indicate that in the case of low-temperature structures a single-temperature high-resolution X-ray measurement may be sufficient if only good quality ADPs are provided. Our latest work shows that application of TAAM refinement to the standard-resolution data for an organic molecule yields ADPs comparable in accuracy to the benchmark charge density modeling.77

In order to verify if there are any differences between the thermal motion and, as a consequence, in vibrational entropy, between the two polymorphic forms for 1 and 2, we have compared the average value of Uiso for non-hydrogen atoms. For polymorphs 1a and 1b, the mean Uiso equals 0.017 and 0.016 Å2, respectively, whereas for 2a and 2b, it amounts to 0.021 and 0.017 Å2, respectively. In the case of the polymorphs of compound 2, there are significant differences in the overall magnitude of the thermal motion, which are also well-visible when comparing differences in ADPs in the form of differential RMSD surfaces (so-called PEANUT plots).78,79 It is clearly seen that, despite the possibly slightly disordered part of the molecule, the overall differences are positive (i.e., ADPs of 2a are on average larger, Figure 10). This indicates that the

Figure 10. PEANUT representation of difference RMSD surface drawn as a difference between 2a and 2b molecules’ ADPs (blue color, positive difference; red, negative; scale of 3.08 was used; hydrogen atoms omitted for clarity).

thermal motion can have an important influence on the relative stability of the two crystal structures. Thus, for both sets of polymorphs (1 and 2), we have decided to take the entropy factor into account. The TLS analyses for all compounds (1a, 1b, 2a, 2b) were conducted with ADPs obtained after the TAAM refinement. The TLS analysis for 1a is relatively simple; thus, the normalmode frequencies were calculated in a straightforward manner. For 1b, which has two symmetry-independent species in the asymmetric unit, the TLS analysis was conducted separately for both molecules. The resulting normal-mode frequencies are comparable to those computed for 1a (Table 4). Consequently, the calculated vibrational entropies for polymorphs 1a and 1b are almost the same, so the entropy factor does not affect their 3109



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contribution from entropy to free energy will be ca. 2.5 kJ· mol−1 higher for 2a. However, as we mentioned in the Experimental Section, such entropy, computed only from Γ point frequencies, is not very accurate (see also Nyman and Day71), and it does not take into account the important contribution arising from the acoustic modes. When we applied the procedure described in the Experimental Section (i.e., the first 24 normal modes and their frequencies from CRYSTAL were replaced by those from TLS), the resulting entropy appeared to be even more in favor for 2a (the difference is 14.5 J·mol−1·K−1; thus, the contribution from entropy to the free energy is ca. 4.5 kJ·mol−1 higher for 2a at room temperature). According to our investigations, the polymorphic system 1 seems to be monotropic. For a monotropic system, free energy curves should not cross at any point. This is the case of form 1a, which seems to be more stable than 1b in the whole temperature range. It is characterized by more advantageous cohesive energy, and the entropy contribution is not sufficient to revert the stability order. 1a is more commonly observed, its crystals are stable under ambient conditions for a considerably long time, and it has a higher melting point. All these findings are in agreement with the DSC curves, which do not reveal any phase transition prior to melting. In turn, a quite different situation is observed for polymorphs 2a and 2b. According to the DSC measurements, this system should also be monotropic, with form 2a being more stable in the whole temperature range. However, the lower cohesive energy value (Table 3) obtained from computations for 2b suggests that form 2b is more stable at low temperatures. As the cohesive energy is referred to the isolated molecule being of different conformation in both polymorphs, this energy difference (about 0.38 kJ·mol−1) is added for polymorph 2b, which makes this form even more energetically stable. Moreover, form 2b crystallizes more often and is more stable at room conditions. On the other hand, form 2a has a higher melting point; hence, at high temperatures 2a seems to be more favorable than 2b. However, it occurs that when the entropic contribution is taken into consideration, at temperatures higher than 65 °C, stability is interchanged in favor of 2a, which explains the higher melting point and ΔHf of 2a with respect to 2b. On the contrary, no phase transition in this region was observed from the DSC measurements and variable temperature XRPD studies (Figures 1S and 2S, Supporting Information). Therefore, we may conclude that there is some kinetic hindrance which cannot be taken into account in our investigations, and which makes phase transition impossible.

Table 4. Vibrational Entropy Values from the TLS Model (STLS) Evaluated for Polymorphs at Two Temperatures (90 and 298 K)a Compd

RTLS

1a

0.11

1bb

0.12

1bc

0.09

2a

0.07

2b

0.09

Normal mode frequencies, υi/cm−1 23.9, 25.3, 31.0, 38.0, 50.0, 55.6 25.2, 26.6, 29.9, 33.8, 47.6, 53.7 27.3, 29.5, 30.1, 36.5, 46.5 61. 7 19.1, 22.6, 29.8, 43.3, 55.6, 129.5, 60.5, 122.2 24.1, 27.4, 30.4, 49, 113.7, 394.2, 42.0, 99.9

−1 −1 −1 −1 K K S90 S298 TLS /J·mol ·K TLS /J·mol ·K

79.0

138.0

80.1

139.1

77.0

136.0

87.1

164.1

78.0

149.9

a

The estimated standard deviation (e.s.d.) values on entropy amount to about 1.0 J·mol−1·K−1. For 2a and 2b the last two frequencies correspond to normal modes for attached groups. bMolecule A (Figure 1). cMolecule B (Figure 1).

relative stabilities. This result was expected, because no significant differences in the mean Uiso values for both forms were observed. A completely different situation is encountered for polymorphs of 2 (i.e., 2a and 2b crystal structures). It appears that, in the case of 2a and 2b, there is a significant difference in the vibrational entropies evaluated with the TLS approach (Table 4), suggesting the entropy contribution to the crystal stability to be larger for 2a than for the 2b polymorph. After the TLS analysis, it occurred that one of the eigenvalues (related to the libration motion) is slightly negative, which prevents further computation of the corresponding frequency values. This wellknown problem has been pointed out by Johnson,80 and it may appear when all atoms are located on a circle, at two coplanar straight lines etc., which was the case of the 2a and 2b crystal structures. Similar investigations were reported by Pal et al.,81 who proposed zeroing of these particular negative eigenvalues. In contrast, we applied the so-called attached rigid group approach (already accessible in the THMA program), allowing introduction of flexibility between two straight fragments of the molecule (note: two libration axes located similarly for each polymorph were defined). We note that for the 2b crystal structure the ADPs for C4, C5, and C6 carbon atoms are slightly elongated, which may suggest some slight unrefineable disorder. However, the chosen libration axes allow for modeling of this elongation properly within the TLS approach, which means that ADPs calculated from the TLS analysis were comparable with those observed from experiment and the final RTLS was quite low. Thus, we were able to obtain normal frequencies within a physically reasonable model, and calculate entropy related to low frequency modes. It has to be stressed that the frequencies calculated for normal modes obtained after the TLS analysis enable us to estimate only a part of the vibrational entropy. Therefore, for compound 2, for which entropy seems to have a significant influence on the relative stability, we decided to look at the total entropy values. The difference in the total entropies computed purely from CRYSTAL frequencies calculated at the Γ point is higher for 2a polymorph by 8.2 J·mol−1·K−1 at room temperature. This means that, at room temperature, the

4. SUMMARY AND CONCLUSIONS Two new biologically active N-acylhydrazones were prepared by condensation of 2-pyridine-carboxaldehyde with the corresponding acid hydrazides. Multiple crystallization experiments resulted in two anhydrous polymorphs and a hydrate for each compound. The single-crystal X-ray data revealed that the structural differences between the polymorphs are related mainly to the orientation of the acyl substituents. This is especially true for 1a and 1b, which differ only in the arrangement of the aromatic substituent with respect to the remaining molecular fragment; thus, they can be treated as conformational polymorphs.82 Structural modifications result in different hydrogen-bonding patterns, which affect the overall crystal packing. It is noteworthy that the acyl substituents are involved solely in 3110



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support (grant No. N N204 546839). KNJ and RK thank the Wrocław Centre for Networking and Supercomputing (grant No. 285) for providing computational facilities.

weak C−H···O, C−H···π interactions, which explains their susceptibility to conformational changes and thus supports the propensity for polymorphic modifications. The association modes of the unsolvated hydrazones are dominated by strong N−H···O or N−H···N hydrogen bonds, involving hydrazide and amide functions. The key feature of those compounds, which might explain the propensity to hydrates formation, is the deficiency of proton-donor groups. The imbalance between the hydrogen bond donor/acceptor atoms can be easily modified through inclusion of water into the crystal. The energy gain due to the built-in water molecules amounts to about 105 kJ·mol−1, when compared to the structures with excluded water moieties, or to about 62 kJ· mol−1 per asymmetric unit confronting the hydrated and anhydrous forms. The hydrated crystals, however, are much less readily formed than the corresponding solvent-free ones. On the other hand, when exposed to air for a long time, the anhydrous forms gradually deteriorate, presumably absorbing water from air. As expected, the studied polymorphic systems are characterized by comparable cohesive energy values which differ only by a couple of kilojoules per mole, on average. In such cases the vibrational entropy factors can be crucial to determine the relative stability of polymorphs, especially at room and higher temperatures. Indeed, although the vibrational entropy values were determined using different approaches than that by Nyman and Day, our results confirm their conclusion and show that for some polymorphic systems entropy contribution cannot be neglected.

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(1) Sacconi, L. J. Am. Chem. Soc. 1953, 75, 5434−5435. (2) Belskaya, N. P.; Dehaen, W.; Bakulev, V. A. Arkivoc 2010, 1, 275−332. (3) Khalil, T. E.; Labib, L.; Iskander, M. F. Polyhedron 1994, 13, 2569−2578. (4) Richardson, R.; Becker, E.; Bernhardt, P. V. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1999, C55, 2102−2105. (5) Paschalidis, D. G.; Tossidis, I. A.; Gdaniec, M. Polyhedron 2000, 19, 2629−2637. (6) Palla, G.; Predieri, G.; Domiano, P.; Vignali, C.; Turner, W. Tetrahedron 1986, 42, 3649−3654. (7) Kitaev, Y. P.; Buzykin, B. I.; Troepolskaya, T. V. Russ. Chem. Rev. 1970, 39, 441−456. (8) Litvinov, I. A.; Kataeva, O. N.; Ermolaeva, L. V.; Vagina, G. A.; Troepolskaya, T. V.; Naumo, V. A. Bull. Acad. Sci. USSR, Div. Chem. Sci. 1991, 40, 62−67. (9) Sugiura, M.; Kabayashi, S. Angew. Chem., Int. Ed. 2005, 44, 5176− 5186. (10) Friestad, G. K. Eur. J. Org. Chem. 2005, 15, 3157−3172. (11) Friestad, G. K.; Draghici, C.; Soukri, M.; Qin, J. J. Org. Chem. 2005, 70, 6330−6338. (12) Singh, R. B. Talanta 1982, 29, 77−84. (13) Katyal, M.; Dutt, Y. Talanta 1975, 22, 151−166. (14) West, D. X.; Liberta, A. E.; Padhye, S. B.; Chikate, R. C.; Sonawane, P. B.; Kumbhar, A. S.; Yerande, R. G. Coord. Chem. Rev. 1993, 123, 49−71. (15) Harinath, Y.; Reddy, D. H. K.; Kumar, B. N.; Lakshmi, K.; Seshaiah, K. J. Chem. Pharm. Res. 2011, 3, 698−706. (16) Savini, L.; Chiasserini, L.; Travagli, V.; Pellerano, C.; Novellino, E.; Cosentino, S.; Pisano, M. B. Eur. J. Med. Chem. 2004, 39, 113−122. (17) Singh, B.; Narang, K. K.; Srivastava, R. Synth. React. Inorg., Met.Org., Nano-Met. Chem. 2003, 33, 1025−1036. (18) Kucukguzel, S. G.; Rollas, S.; Kucukguzel, I.; Kiraz, M. Eur. J. Med. Chem. 1999, 34, 1093−1100. (19) Rodriguez-Arguelles, M. C.; Vazques, S. M.; Touceda, P. T.; Matalobos, J. S.; Deibe, A. M. G.; Ferrari, M. B.; Polesi, G.; Pelizzi, C.; Zanil, F. J. Inorg. Biochem. 2007, 101, 138−147. (20) Patole, J.; Sandbhor, U.; Padhye, S.; Deobagkar, D. N.; Anson, C. E.; Powell, A. Bioorg. Med. Chem. Lett. 2003, 13, 51−55. (21) Easmon, J.; Puerstinger, G.; Roth, T.; Fiebig, H. H.; Jenny, M.; Jaeger, W.; Heinisch, G.; Hofmann, J. Int. J. Cancer 2001, 94, 89−96. (22) Shrivastav, A.; Singh, N. K.; Tripathi, P.; George, T.; Dimmock, J. R.; Sharma, R. K. Biochimie 2006, 88, 1209−1216. (23) Ainscough, E. W.; Brodie, A. M.; Denny, W. A.; Finlay, G. J.; Gothe, S. A.; Ranford, J. D. J. Inorg. Biochem. 1999, 77, 125−133. (24) Junior, W. B.; Alexandre-Moreira, M. S.; Alves, M. A.; PerezRebolledo, A.; Parrilha, G. L.; Castellano, E. E.; Piro, O. E.; Barreiro, E. J.; Lima, L. M.; Beraldo, H. Molecules 2011, 16, 6902−6915. (25) Tributino, J. L. M.; Duarte, C. D.; Correa, R. S.; Doriguetto, A. C.; Ellena, J.; Romeiro, N. C.; Castro, N. G.; Miranda, A. L. P.; Barreiro, E. J.; Fraga, C. A. M. Bioorg. Med. Chem. 2009, 17, 1125− 1131. (26) Bernhardt, P. V.; Chin, P.; Sharpe, P. C.; Wang, J. Y. C.; Richardson, D. R. JBIC, J. Biol. Inorg. Chem. 2005, 10, 761−777. (27) Bernhardt, P. V.; Chin, P.; Sharpe, P. C.; Richardson, D. R. Dalton Trans. 2007, 30, 3232−3244. (28) Mazur, L.; Jarzembska, K. N.; Kamiński, R.; Woźniak, K.; Pindelska, E.; Zielińska-Pisklak, M. Cryst. Growth Des. 2014, 14, 2263− 2281. (29) Agilent Technologies. CRYSALIS PRO; Yarnton, Oxfordshire, England, UK, 2013. (30) Blessing, R. H. J. Appl. Crystallogr. 1997, 30, 421−426. (31) Blessing, R. H. Crystallogr. Rev. 1987, 1, 3−58.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.cgd.5b01673. Synthetic, physicochemical and spectral characteristics of all studied crystals, supporting crystallographic data and TAAM refinement details, selected geometric parameters after TAAM refinement, geometries of hydrogen bonds with interaction energy values of selected molecular dimers, theoretical calculations of NMR shielding constants in CASTEP, 13C and 15N NMR chemical shifts with detailed discussion of solid-state NMR data, additional TGA-DSC experiments, and variable temperature XRPD patterns for 2b (PDF) Accession Codes

CCDC 1406086−1406091 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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REFERENCES

AUTHOR INFORMATION

Corresponding Author

*Liliana Mazur. E-mail: [email protected]. Telephone: (+48) 815375743. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS LM would like to thank the Polish Ministry of Science and Higher Education/National Science Centre for financial 3111



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(32) Sheldrick, G. M. Acta Crystallogr., Sect. A: Found. Crystallogr. 2008, A64, 112−122. (33) Jarzembska, K. N.; Kubsik, M.; Kamiński, R.; Woźniak, K.; Dominiak, P. M. Cryst. Growth Des. 2012, 12, 2508−2524. (34) Bąk, J. M.; Domagała, S.; Hübschle, C.; Jelsch, C.; Dittrich, B.; Dominiak, P. M. Acta Crystallogr., Sect. A: Found. Crystallogr. 2011, A67, 141−153. (35) Koritsanszky, T.; Volkov, A.; Coppens, P. Acta Crystallogr., Sect. A: Found. Crystallogr. 2002, A58, 464−472. (36) Volkov, A.; Li, X.; Koritsanszky, T.; Coppens, P. J. Phys. Chem. A 2004, 108, 4283−4300. (37) Dittrich, B.; Hübschle, C. B.; Holstein, J. J.; Fabbiani, F. P. A. J. Appl. Crystallogr. 2009, 42, 1110−1121. (38) Pröpper, K.; Holstein, J. J.; Hübschle, C. B.; Bond, C. S.; Dittrich, B. Acta Crystallogr., Sect. D: Biol. Crystallogr. 2013, D69, 1530−1539. (39) Dittrich, B.; Koritsanszky, T.; Luger, P. Angew. Chem., Int. Ed. 2004, 43, 2718. (40) Jelsch, C.; Guillot, B.; Lagoutte, A.; Lecomte, C. J. Appl. Crystallogr. 2005, 38, 38−54. (41) Jarzembska, K. N.; Dominiak, P. M. Acta Crystallogr., Sect. A: Found. Crystallogr. 2012, A68, 139−147. (42) Jarzembska, K. N.; Kamiński, R.; Wenger, E.; Lecomte, C.; Dominiak, P. M. J. Phys. Chem. C 2013, 117, 7764−7775. (43) Hansen, N. K.; Coppens, P. Acta Crystallogr., Sect. A: Cryst. Phys., Diffr., Theor. Gen. Crystallogr. 1978, A34, 909−921. (44) Allen, F. H. Acta Crystallogr., Sect. B: Struct. Sci. 2002, B58, 380− 388. (45) Advanced Chemistry Development Inc. ACD/SpecMenager; 2007. (46) Segall, M. D.; Lindan, P. J. D.; Probert, M. J.; Pickard, C. J.; Hasnip, P. J.; Clark, S. J.; Payne, M. C. J. Phys.: Condens. Matter 2002, 14, 2717−2744. (47) Accelrys; 2011. (48) Tkatchenko, A.; Scheffler, M. Phys. Rev. Lett. 2009, 102, 073005. (49) Pickard, C. J.; Mauri, F. Phys. Rev. B: Condens. Matter Mater. Phys. 2001, 63, 245101. (50) Becke, A. D. Phys. Rev. A: At., Mol., Opt. Phys. 1988, 38, 3098− 3100. (51) Perdew, J. P. Phys. Rev. B: Condens. Matter Mater. Phys. 1986, 33, 8822−8824. (52) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B: Condens. Matter Mater. Phys. 1988, 37, 785−789. (53) Krishnan, R.; Binkley, J. S.; Seeger, R.; Pople, J. A. J. Chem. Phys. 1980, 72, 650−654. (54) Grimme, S. J. Comput. Chem. 2004, 25, 1463−1473. (55) Grimme, S. J. Comput. Chem. 2006, 27, 1787−1799. (56) Civalleri, B.; Zicovich-Wilson, C. M.; Valenzano, L.; Ugliengo, P. CrystEngComm 2008, 10, 405−410. (57) Boys, S. F.; Bernardi, F. Mol. Phys. 1970, 19, 553−566. (58) Civalleri, B.; Doll, K.; Zicovich-Wilson, C. M. J. Phys. Chem. B 2007, 111, 26−33. (59) Maschio, L.; Civalleri, B.; Ugliengo, P.; Gavezzotti, A. J. Phys. Chem. A 2011, 115, 11179−11186. (60) Kamiński, R.; Jarzembska, K. N.; Domagała, S. J. Appl. Crystallogr. 2013, 46, 540−534. (61) Schomaker, V.; Trueblood, K. N. Acta Crystallogr., Sect. B: Struct. Sci. 1998, B54, 507−514. (62) Schomaker, V.; Trueblood, K. N. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1968, B24, 63−76. (63) Cruickshank, D. W. J. Acta Crystallogr. 1956, 9, 754−756. (64) Sands, D. E. Vectors and Tensors in Crystallography; AddinsonWesley Publishing Company: 1982. (65) Madsen, A. Ø.; Larsen, S. Angew. Chem., Int. Ed. 2007, 46, 8609−8613. (66) Pascale, F.; Zicovich-Wilson, C. M.; Gejo, F. L.; Civalleri, B.; Orlando, R.; Dovesi, R. J. Comput. Chem. 2004, 25, 888−897. (67) Madsen, A. Ø.; Civalleri, B.; Ferrabone, M.; Pascale, F.; Erba, A. Acta Crystallogr., Sect. A: Found. Crystallogr. 2013, A69, 309−321.

(68) Willis, B. T. M.; Pryor, A. W. Thermal vibrations in crystallography; Cambridge University Press: London, 1975. (69) Wardell, S. M. S. V.; de Souza, M. V. N.; Wardell, J. L.; Low, J. N.; Glidewell, C. Acta Crystallogr., Sect. B: Struct. Sci. 2007, B63, 879− 895. (70) Aakeröy, C. B.; Forbes, S.; Desper, J. CrystEngComm 2012, 14, 2435−2443. (71) Nyman, J.; Day, G. M. CrystEngComm 2015, 17, 5154−5165. (72) Aree, T.; Bürgi, H.-B. J. Phys. Chem. A 2012, 116, 8092−8099. (73) Aree, T.; Bürgi, H.-B. J. Phys. Chem. B 2006, 110, 26129−26134. (74) Capelli, S. C.; Förtsch, M.; Bürgi, H.-B. Acta Crystallogr., Sect. A: Found. Crystallogr. 2000, A56, 413−424. (75) Bürgi, H.-B.; Capelli, S. C. Acta Crystallogr., Sect. A: Found. Crystallogr. 2000, A56, 403−412. (76) Madsen, A. Ø.; Mattson, R.; Larsen, S. J. Phys. Chem. A 2011, 115, 7794−7804. (77) Jarzembska, K. N.; Hoser, A. A.; Kamiński, R.; Madsen, A. Ø.; Durka, K.; Woźniak, K. Cryst. Growth Des. 2014, 14, 3453−3465. (78) Hummel, W.; Hauser, J.; Bürgi, H.-B. J. Mol. Graphics 1990, 8, 214−220. (79) Hummel, W.; Raselli, A.; Bürgi, H.-B. Acta Crystallogr., Sect. B: Struct. Sci. 1990, B46, 683−692. (80) Johnson, C. K. In Crystallographic computing; Ahmed, F. R., Ed. Munksgaard: Copenhagen, 1970; pp 201−229. (81) Pal, R.; Madhusudana Reddy, M. B.; Dinesh, B.; Balaram, P.; Guru Row, T. N. J. Phys. Chem. A 2014, 118, 9568−9574. (82) Cruz-Cabeza, A. J.; Bernstein, J. Chem. Rev. 2014, 114, 2170− 2191.

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