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Article

Synthesis, Structural Characterization, Conformational and Topological Classification of Different Salts in the 2,2-Dimethylpropane-1,3-diamine/HCl/H2O-System

by
Jaqueline Heimgert
1,
Florian Morsbach
1,
Martin Kleinschmidt
2 and
Guido J. Reiss
1,*
1
Institut für Anorganische Chemie und Strukturchemie, Lehrstuhl II Material-und Strukturforschung, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, D-40225 Düsseldorf, Germany
2
Institut für Theoretische Chemie und Computerchemie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, D-40225 Düsseldorf, Germany
*
Author to whom correspondence should be addressed.
Solids 2022, 3(3), 385-396; https://doi.org/10.3390/solids3030027
Submission received: 9 May 2022 / Revised: 15 June 2022 / Accepted: 16 June 2022 / Published: 28 June 2022
Browse Figures
Versions Notes

Abstract

:
The reaction of 2,2-dimethylpropane-1,3-diamine (dmpn) with an excess of concentrated aqueous hydrochloric acid yielded colorless crystals of 2,2-dimethylpropane-1,3-diaminium dichloride, dmpnH2Cl2 (1), in addition to small amounts of a monohydrate, dmpnH2Cl2∙H2O (2). The compounds were studied via X-ray crystallography, IR and Raman spectroscopy, NMR spectroscopy and thermal analysis. Single crystal structure determinations on 1 and 2 showed that dmpnH2Cl2 exists in two polymorphic forms, 1a and 1b. The crystal structure of 1b showed to be much more complex than that of 1a. In the crystal structure of 2, four (dmpnH2)2+ cations and eight chloride anions form a cage constructed by N−H∙∙∙Cl hydrogen bonds. In the center of these cages water dimers with a O∙∙∙O distance of 2.776 (8) Å are present. In addition, a conformational analysis of the 2,2-dimethylpropane-1,3-diaminium cation was performed. The results are compared to the experimental findings of 1a, 1b, 2 and other related hydrogen bonded salt structures from the Cambridge crystallographic structure database (CCDC). Last, a topological classification of the solid-state structures of 1a and 2 was performed and the simplified topological networks are discussed.

1. Introduction

Generally, 2,2-dimethylpropane-1,3-diamine (dmpn) is easily accessible through the reduction of 1,3-dinitro-2,2-dimethylpropane with iron in high yields [1]. The synthetic protocol of dmpn has been optimized and was applied for patent in 1973 [2]. With transition metals dmpn forms stable complexes [3,4,5,6]. Consequently, dmpn and ligands with a similar topology have a broad scope application such as their use as bridging ligands in metal organic frameworks and in coordination polymers [7,8]. Recently we reported the interesting finding that dmpn is able to capture CO2 spontaneously by the formation of (3-ammonio-2,2-dimethyl-propyl)carbamate dihydrate [9]. The carbamate releases its CO2 on heating which might add some applications.
The crystal structures of different salt-like compounds containing the di-protonated dmpn are accessible [7,10,11,12,13,14,15,16,17]. In total sixteen related structures can be found in the CSD [18]. Since the crystal structures of dmpn dihydrobromide [11], dmpn dihydroiodide [11] as well as dmpn dihydroiodide−iodide (1/1) have already been determined [12] it is wondrous that no crystal structure of the respective dihydrochloride has been published until now. We were able to characterize three different phases in the dmpn/HCl/H2O-system (Figure 1). The crystal structures of two polymorphic forms of dmpn dihydrochloride (1a and 1b), and of dmpn dihydrochloride monohydrate (2), have been determined. The structures of 1a and 1b differ strongly from each other and 1a will be discussed in detail, while 1b only has been deposited as a CSD communication [19], as its structure turned out to be very complex, with a large Z and a hydrogen bonded network that does not easily fit into a simple architecture of hydrogen bonds [20,21]. To get an impression of the forces that mainly contribute to the solid-state structures containing the 2,2-dimethylpropane-1,3-diaminium cation [(dmpnH2)2+], a conformational analysis was performed to compare the intramolecular interactions in terms of intermolecular interactions such as charge supported hydrogen bonding and van der Waals forces in the crystal structures of: dmpnH2Cl2 (1a and 1b [19]), dmpnH2Cl2∙H2O (2), dmpnH2Br2 [11], dmpnH2I2 [11], dmpnH2I2I2 [12], dmpnH2(NO3)2 [13], dmpnH2(CrO4) [14], dmpnH2[ZnCl4] [15], dmpnH2[CdBr4] [16], and dmpnH2[InBr4][InBr11] [17].

2. Materials and Methods

2.1. Synthesis

All chemicals were obtained from commercial sources and used as purchased. 10 mL of conc. hydrochloric acid (~120 mmol) was added dropwise to 3.07 g of 2,2-dimethylpropane-1,3-diamine (30 mmol). After complete neutralization of the amine by the hydrochloric acid, the HCl concentration in the obtained solution was approximately 6 mol·L−1. This clear, colorless solution was left in a fume hood for two weeks until the liquid had completely evaporated. Yield: 4.83 g = 92% (calc. for C5H16N2Cl2), colorless solid. A CHN analysis was performed with a vario MICRO cube [22]. Analysis calculated for C5H16N2Cl2 [%]: C 34.30, H 9.21, N 16.00; found: C 34.12, H 9.09, N 15.74. 1H- and 13C{1H}-NMR-spectra were recorded with a Bruker Avance III spectrometer and analyzed with the MestReNova software package [23]. 1H-NMR (500 MHz, D2O) δ [ppm]: 1.17 (s, 6H, CH3), 3.05 (s, 4H, CH2). 13C{1H}-NMR (75 MHz, D2O) δ [ppm]: 21.21 (CH3), 32.35 (CH2), 46.83 (C). Single crystals of 2,2-dimethylpropane-1,3-diaminium dichloride (1a and 1b) and of 2,2-dimethylpropane-1,3-diaminium dichloride monohydrate (2), suitable for crystal structure analysis were selected directly from the bulk material. The main phase turned out to be 1a, while 1b and 2 appear as by-products in small quantities. Since the crystals could not be clearly distinguished from each other morphologically, several single crystals were checked via X-ray diffraction and these were separated into three fractions 1a, 1b and 2 by hand based on their lattice parameters and used for further analysis. The ratio of 1a to the sum of 1b and 2 is estimated to be five to ten.

2.2. IR-and Raman Spectroscopy

IR spectra of 1a, 1b and 2 were recorded with a PerkinElmer Spectrum Two FT-IR spectrometer, equipped with a LiTaO3 detector (4000–350 cm−1) and an universal ATR unit [24,25]. IR spectrum of 1a/1b [cm−1]: ν(N−H): ~3045 (sh); ν(C−H): 2895 (s, br); 2710 (m); 2607 (m); 2014 (w); δ(N−H): 1593 (m), 1514 (s); δ(C−H): 1472 (m). IR spectrum of 2 [cm−1]: ν(O−H): 3509, 3439, 3366 (m); ν(N−H): ~3035 (sh); ν(C−H): 2912 (s, br); 2610 (m); 2051 (w); δ(N−H): 1588, 1575 (m), 1512 (s); δ(C−H): 1472, 1459 (m).
Raman spectra of 1a, 1b and 2 were recorded with a Bruker MultiRAM FT Raman spectrometer, equipped with a Nd:YAG laser (1064 nm) and a InGaAs detector (4000–70 cm−1) [26]. Raman spectrum of 1a/1b [cm−1]: ν(N−H): 3050 (m); ν(C−H): 2978, 2904 (s); 2835 (m); 2735, 2615 (w); δ+(N−H): 1601 (w), 1512 (m); δ(C−H): 1481, 1446 (m); δ(CH2): 725 (s). Raman spectrum of 2 [cm−1]: ν(O−H): 3363 (w); ν(N−H): 3066 (m); ν(C−H): 2966, 2900 (s); 2827, 2753 (m); δ(N−H): 1569 (w), 1516 (m); δ(C−H): 1473 (s), 1434 (m); δ(CH2): 733 (s).
Assignments were made according to [27,28]. The bands and lines below 1400 cm−1 are less instructive and are not listed, with the exception of the characteristic CH2 rocking mode. The CH2 rocking mode at ~720 cm−1 is IR inactive (see Raman spectra).
A comparison to the IR and Raman spectra of dmpn can be found in Figure 2.

2.3. Thermal Analysis

Compounds 1a and 2 were characterized by DSC/TGA thermal analysis. DSC curves were recorded under N2 atmosphere with a heating/cooling rate of 5 K·min−1 in the temperature range of 25–200 °C with a Mettler-Toledo DSC 1 STARe system. The DSC curves of 1a and 2 (see Figure 3) show a similar appearance except for a series of endothermic features in the range of 55–135 °C, mostly related to the loss of water. The mass of 2 decreases by ~10% (calc. 9.3% for C5H16N2Cl2 H2O). Both compounds, 1a and 2, show two further endothermic features in their heating curves at ~138 °C and ~145 °C (peak maxima). The cooling curves each show two exothermic features at ~140 °C and ~125 °C (peak maxima). The shoulder at ~120 °C in the cooling curve of 1a cannot be clearly assigned (see Figure 3). These observations suggest at least two reversible phase transitions and a common high-temperature phase of the substances. A TGA curve of the ‘dried’ material from the DSC measurements was recorded under N2 atmosphere with a heating rate of 5 K·min−1 in the temperature range of 20–600 °C with a Netsch STA 449C device. A mass loss of ~98% in the range of 250–400 °C (Tonset = 250 °C) is compatible to the complete decomposition of the sample.

2.4. Crystal Structure Analysis

The single crystal diffraction data of 1a, 1b, and 2 were collected with a Xcalibur Eos diffractometer. Indexing, unit cell refinement data collection and data processing followed the standard procedures of the CrysAlisPRO software package [29]. A multi-scan absorption correction was applied for 1a and 2 with the SCALE3 ABSPACK routine of CrysAlisPRO [29], and an analytical absorption correction was applied for 1b [30]. The structure solution with Direct Methods and the structure refinement by full-matrix least-squares calculations on F2 were carried out with programs of the SHLEX family [31,32,33]. After all non-hydrogen atoms have been located, H atoms bound to C and N were included in idealized positions using a riding model with bond lengths constrained to 0.96, 0.97, and 0.89 Å for CH3, CH2 and NH3, respectively. In addition, the CH3 and NH3 groups were allowed to rotate around the adjacent C−C bond. The displacement parameters Uiso(H) of the H atoms bound to C and N were set to 1.5Ueq, 1.2Ueq, and 1.5Ueq of the parent atoms for CH3, CH2 and NH3, respectively. Crystals of 1b and 2 suffered from twinning and were refined as 2-component twins with the HKLF5 option of SHELXL. The fractions of second individual contribution were refined to 0.335 and 0.404 for 1b and 2, respectively. Molecular graphics were generated with DIAMOND [34]. Crystal data, data collection and structure refinement details for 1a, 1b and 2 are given in Table 1.

3. Results

3.1. Structural Commentary

Compound 1a crystallizes in the monoclinic space group C2/c (Z = 8). The asymmetric unit contains one dmpn cation [(dmpnH2)2+] and two chloride anions (all in general positions). The structure forms layers along the crystallographic a-axis (see Figure 4). Each layer consists of strands, each of which contains two symmetry related cations arranged around a center of inversion. Both aminium groups of the cations and the chloride anions are involved into a N−H∙∙∙Cl hydrogen-bonded network. The geometrical parameters of all hydrogen bonds are given in Table 2. All N∙∙∙Cl distances are in narrow ranges of 3.146 (1)–3.180 (1) Å [35]. There are others in the range of 3.272 (1)–3.336 (1) Å which are significantly weaker. Obviously, the cations show an unsymmetrical hydrogen bonding pattern. The aminium group including N1 forms three hydrogen bonds to chloride anions within the same strand. The aminium group including N2 forms one hydrogen bond to a chloride anion within the same strand and one hydrogen bond to the adjacent strand, causing the connection between the strands. No N−H∙∙∙Cl hydrogen bonds could be identified between adjacent layers along the crystallographic a-axis. Consequently, they are connected by van der Waals forces and non-classical C−H∙∙∙Cl hydrogen bonds.
Compound 2 crystallizes in the triclinic space group P 1 ¯ (Z = 2). The asymmetric unit contains one cation [(dmpnH2)2+] and two chloride anions (all in general positions). Four symmetry related formula units each form a cavity with two water molecules inside (see Figure 4). These two water molecules build a dimer arranged around a center of inversion in the middle of the cavity. They are connected by a classical O−H∙∙∙O hydrogen bond with a O1∙∙∙O2 distance of 2.776 (8) Å. Thus, the cavity is too large for only one water dimer the structure refinement suggests that there are two energetically identical positions for this water dimer which are each half occupied. In general, eight hydrogen bonds caused by aminium groups, and three hydrogen bonds caused by the water molecules can be identified. The geometrical parameters of these hydrogen bonds are given in Table 1. All N∙∙∙Cl distances are in narrow ranges of 3.173 (2)–3.318 (3) Å [35]. The hydrogen bonds of N1–H11 and N2–H22 are bifurcated and their N∙∙∙Cl distances are significantly longer than those of the other ones. The half-occupied water molecules including O1 and O2 each form two O−H∙∙∙Cl hydrogen bonds with chloride anions.

3.2. Conformational Analysis

A theoretical conformational analysis of the 2,2-dimethylpropane-1,3-diaminium cation was performed. As shown in Figure 5, six conformations can be postulated for the rotation of the amino group including N1 around the N1C1–C2C3 bond. The eclipsed conformations with the dihedral torsion angle Θ at 0° (syn), +120° and −120° (=+240°) are conformers with maximum energies. The staggered conformations with Θ at +60° (gauche) and −60° (=+300°) as well as 180° (anti) are conformers with minimum energies. Assuming that the two amino groups do not interact with each other, the same ideas can be applied for the rotation of the amino group including N2 around the C1C2−C3N2 bond.
In order to get a qualitative impression of the energy landscape for the rotation of the two amino groups in the (dmpnH2)2+ cation, quantum chemical calculations have been performed. The Turbomole [36] suite of programs was used at the density functional theory (DFT) level with B3-LYP functional and the def-SV(P) basis set in the gas phase. Constrained geometry optimizations have been performed on a 2-dimensional grid. The N1C1–C2C3 angle has been scanned from 0 to 360° in steps of 5°, the C1C2−C3N2 angle from 20 to 180° in steps of 5° (10° in the range of 20–50°). The values for this angle from 180 to 340° have been obtained by symmetry. The scan reveals the anti-anti-conformation [Θ1/Θ2: 180°/180° (aa)] to be the global minimum (see Figure 6). In this conformation, the atoms N1, C1, C2, C3, and N2 are all in-plane. Barriers of 21 kJ·mol−1 (read from the grid) lead to four equivalent local minima for the anti-gauche-conformations [Θ1/Θ2: 180°/+60° (ag), 180°/−60° (a–g), +60°/180° (ga), −60°/180° (−ga)]. These correspond to one of the amino groups being turned up or down from the C1-C2-C3 plane. An unconstrained optimization of these structures yields angles of 173°/76° and an energy of 13 kJ·mol−1 above the conformational ground state. Inspecting the four gauche-gauche-combinations [Θ1/Θ2: +60°/+60° (gg), +60°/−60° (g–g), −60°/+60° (–gg), −60°/−60° (–g–g)], two pairs of equivalent structures can be found. The first pair corresponds to turning the two amino groups in opposite directions. An optimization puts this conformation at 80.1°/80.1°, 25 kJ·mol−1 above the conformational ground state. The barrier connecting these g/g minima to the a/g minima is at 31 kJ·mol−1 above the conformational ground state or only 6 kJ·mol−1 above the g/g minimum. The second pair corresponds to both amino groups turned in the same direction. Here, no minimum is found on the grid but only a saddle point at 100°/270°, 52 kJ·mol−1 above the conformational ground state.
The experimental torsion angles of the (dmpnH2)2+ cation in the crystal structures of dmpnH2Cl2 (1a and 1b [19]), dmpnH2Cl2∙H2O (2), dmpnH2Br2 [11], dmpnH2I2 [11], dmpnH2I2I2 [12], dmpnH2(NO3)2 [13], dmpnH2(CrO4) [14], dmpnH2[ZnCl4] [15], dmpnH2[CdBr4] [16] and dmpnH2[InBr4][InBr11] [17] are summarized in Table 3.

3.3. Topological Classification

The aminium groups together with the chloride ions form supramolecular hydrogen bonded networks in their crystal structures. Using the ToposPro software package [37] the topology of these networks can be classified using the concept of the simplified underlying net [38]. Figure 7a shows the simplified network of 1a, which can be assigned to the class cbs/CrB (chromium boride type) [37,39,40]. Three different types of interconnected strands can be identified, which are colored orange, blue and pink for discussion. Each strand consists of distorted rectangles, each formed by two N and two Cl atoms. The arrangement guaranties alternating occurrence of aminium groups and chloride anions. Thus, each N atom is surrounded by four Cl atoms and vice versa. The rectangles within a strand are folded in a stair-like manner. The orange-colored strands are crossed by the pink- and the blue-colored strands, while pink- and blue-colored strands never cross (see Figure 7a). Figure 7b shows the simplified network of 2. The topological net can be assigned to the class tcs (thorium chromium silicide type) [41,42,43,44,45,46,47]. It consists of two different types of dodecahedra, which are colored orange and blue for discussion. These polyhedra show a significant distortion of their hexagonal faces, whose angles deviate from the ideal value of 120°. While the orange-colored polyhedra are stretched along the crystallographic c-axis with an N∙∙∙Cl∙∙∙N angle of 147.2°, the angle for the blue-colored polyhedra is 108.1°. The individual disorder of the water dimers contained in the blue-colored polyhedra seems to be determined by the fact that this type of polyhedra is elongated along the crystallographic b-axis. Within one layer, polyhedra of the same type form a columnar connection pattern, where the connection is established by the hexagonal faces along the crystallographic a-axis. Along the crystallographic c-axis, the polyhedron types alternate and are connected by further hexagonal faces (see Figure 7b).

4. Conclusions

In this work, two new salts in the dmpn/HCl/H2O-system have been synthesized and characterized by crystal structure analysis, spectroscopic methods, thermal analysis, and topological classification. Thus, the series of reported halide salts of dmpn has been extended. Phases 1a and 2 show reversible phase transformations at the same temperatures, indicating that a common high-temperature phase of them exists. This could hold potential for further research. A comparison of the crystal structures of 1a, 1b, 2 and further salts from the CSD [18], revealed that the energetically favorable anti-anti-conformer is not always the best option for the 2,2-dimethylpropane-1,3-diaminium cation in the solid state [11,12,13,14,15,16,17,19]. The conformational analysis, which was supported by quantum chemical calculations, verified that the anti-anti-conformation represents the global minimum on the potential energy surface. In some cases, the anti-gauche- and the gauche-gauche-conformation are preferred (see Table 3), obviously due to the formation of hydrogen bonds within the corresponding solid-state structures. The most interesting finding is certainly the caging of water dimers in 2. This particular property of the dmpn/HX/H2O-system may enable the caging of other small molecules such as Br2, IF, IBr, and ICl. By using aliphatic diamines with extended alkyl chains, it might be possible to enlarge the cavity observed in 2 to cage polyiodide chains, such as [I6]2− [48].

Author Contributions

G.J.R. initialized and supervised this project; J.H. and F.M. realized the experiments and prepared the original draft of the manuscript; M.K. performed the quantum chemical calculations. All authors, J.H., F.M., M.K. and G.J.R., contributed significantly to the final draft of the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

Deutsche Forschungsgemeinschaft: INST 208/533-1, project no. 162659349; Open-Access-Fonds of Heinrich-Heine-University Düsseldorf: ULBD-22-.

Acknowledgments

The authors thank Eleonore Hammes, Peter Roloff and Daniel Mombers for technical support.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Formation of the three salts in the 2,2-dimethylpropane-1,3-diamine/HCl/H2O-system described in this work: 2,2-dimethylpropane-1,3-diaminium dichloride (1a and 1b), dmpnH2Cl2, and 2,2-dimethylpropane-1,3-diaminium dichloride monohydrate (2), dmpnH2Cl2·H2O.
Figure 1. Formation of the three salts in the 2,2-dimethylpropane-1,3-diamine/HCl/H2O-system described in this work: 2,2-dimethylpropane-1,3-diaminium dichloride (1a and 1b), dmpnH2Cl2, and 2,2-dimethylpropane-1,3-diaminium dichloride monohydrate (2), dmpnH2Cl2·H2O.
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Figure 2. IR and Raman spectra of dmpn (blue lines), 1a (green lines) and 2 (red lines). The IR bands and the Raman lines between 3400 and 3200 cm−1 in the spectra of dmpn are caused by NH-valence modes of the free amine and are no longer detected in the product spectra. The aminium groups in 1a and 2 are involved in electrostatically supported hydrogen bonds and the bands of their NH-valence modes are broad and significantly shifted to lower wave numbers, overlapping with the CH-valence modes between 2800 and 3000 cm−1. The presence of water in 2 is indicated by the band of the OH-valence modes between 3600 and 3300 cm−1. The respective signal in the Raman spectrum is of very low intensity.
Figure 2. IR and Raman spectra of dmpn (blue lines), 1a (green lines) and 2 (red lines). The IR bands and the Raman lines between 3400 and 3200 cm−1 in the spectra of dmpn are caused by NH-valence modes of the free amine and are no longer detected in the product spectra. The aminium groups in 1a and 2 are involved in electrostatically supported hydrogen bonds and the bands of their NH-valence modes are broad and significantly shifted to lower wave numbers, overlapping with the CH-valence modes between 2800 and 3000 cm−1. The presence of water in 2 is indicated by the band of the OH-valence modes between 3600 and 3300 cm−1. The respective signal in the Raman spectrum is of very low intensity.
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Figure 3. DSC curves (top) of 1a (green lines) and 2 (red lines) and TGA/DTA curve of the ‘dried’ material from the DSC measurements (bottom). 2 loses water between 55 and 135 °C and behaves similar to 1a from this point on. Two reversible phase transitions at ~139 °C and ~145 °C (heating curves) indicate a common high-temperature phase of the substances. The mass loss between 250 and 400 °C is compatible with the complete decomposition of the sample to amine and HCl.
Figure 3. DSC curves (top) of 1a (green lines) and 2 (red lines) and TGA/DTA curve of the ‘dried’ material from the DSC measurements (bottom). 2 loses water between 55 and 135 °C and behaves similar to 1a from this point on. Two reversible phase transitions at ~139 °C and ~145 °C (heating curves) indicate a common high-temperature phase of the substances. The mass loss between 250 and 400 °C is compatible with the complete decomposition of the sample to amine and HCl.
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Figure 4. Sections of the crystal structures, showing the layered arrangement of dmpnH2Cl2 along the crystallographic a-axis in 1a (a), and the cavity containing a water dimer in 2 (b). Displacement ellipsoids are drawn at the 50% probability level; H atoms are drawn with an arbitrary radius. The direction of hydrogen bonds is given by blue dotted lines; the direction of further N−C bonds by truncated sticks. For the sake of clarity, the C atoms belonging to the chosen asymmetric unit are drawn in black. [Symmetry codes for 1a: (i) 1/2−x, 1/2−y, 1−z; (ii) 1/2−x, 3/2−y, 1−z; (iii) x, 1−y, z−1/2. Symmetry codes for 2: (i) 1−x, −y, 1−z; (ii) 1−x, 1−y, 2−z; (iii) −x, −y, 1−z; (iv) 1−x, 2−y, 2−z; (v) 1−x, 1−y, 1−z; (vi) 2−x, 2−y, 2−z; (vii) x, y+1, z; (viii) −x, 1−y, 1−z]. In 1a two symmetry-related (dmpnH2)2+ cations each are arranged around a center of inversion (4c Wyckoff site). The strands are connected by N−H∙∙∙Cl hydrogen bonds while adjacent layers (viewing direction) are connected by non-classical C−H∙∙∙Cl hydrogen bonds and van der Waals forces.
Figure 4. Sections of the crystal structures, showing the layered arrangement of dmpnH2Cl2 along the crystallographic a-axis in 1a (a), and the cavity containing a water dimer in 2 (b). Displacement ellipsoids are drawn at the 50% probability level; H atoms are drawn with an arbitrary radius. The direction of hydrogen bonds is given by blue dotted lines; the direction of further N−C bonds by truncated sticks. For the sake of clarity, the C atoms belonging to the chosen asymmetric unit are drawn in black. [Symmetry codes for 1a: (i) 1/2−x, 1/2−y, 1−z; (ii) 1/2−x, 3/2−y, 1−z; (iii) x, 1−y, z−1/2. Symmetry codes for 2: (i) 1−x, −y, 1−z; (ii) 1−x, 1−y, 2−z; (iii) −x, −y, 1−z; (iv) 1−x, 2−y, 2−z; (v) 1−x, 1−y, 1−z; (vi) 2−x, 2−y, 2−z; (vii) x, y+1, z; (viii) −x, 1−y, 1−z]. In 1a two symmetry-related (dmpnH2)2+ cations each are arranged around a center of inversion (4c Wyckoff site). The strands are connected by N−H∙∙∙Cl hydrogen bonds while adjacent layers (viewing direction) are connected by non-classical C−H∙∙∙Cl hydrogen bonds and van der Waals forces.
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Figure 5. Newman projections for possible conformations of the 2,2-dimethylpropane-1,3-diaminium cation resulting by the rotation of the amino groups including N1 and N2 around the C1–C2 bond and the C2–C3 bond, respectively. The anti-periplanar conformation is expected to be the most stable conformation with minimum energy.
Figure 5. Newman projections for possible conformations of the 2,2-dimethylpropane-1,3-diaminium cation resulting by the rotation of the amino groups including N1 and N2 around the C1–C2 bond and the C2–C3 bond, respectively. The anti-periplanar conformation is expected to be the most stable conformation with minimum energy.
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Figure 6. Potential energy surface for the rotation of the two amino groups in the (dmpnH2)2+ cation, obtained by quantum chemical calculations, showing a global minimum for the anti-anti-conformer (0 kJ·mol−1), a set of four equivalent local minima for the anti-gauche-conformers (13 kJ·mol−1), a set of two equivalent local minima for the gauche-gauche-conformers (25 kJ·mol−1) with the two amino groups oriented in opposite directions, and finally two saddle points for the gauche-gauche-conformers (52 kJ·mol−1) with the two amino groups oriented in the same direction.
Figure 6. Potential energy surface for the rotation of the two amino groups in the (dmpnH2)2+ cation, obtained by quantum chemical calculations, showing a global minimum for the anti-anti-conformer (0 kJ·mol−1), a set of four equivalent local minima for the anti-gauche-conformers (13 kJ·mol−1), a set of two equivalent local minima for the gauche-gauche-conformers (25 kJ·mol−1) with the two amino groups oriented in opposite directions, and finally two saddle points for the gauche-gauche-conformers (52 kJ·mol−1) with the two amino groups oriented in the same direction.
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Figure 7. Topological nets, showing three different kinds of connected strands in 1a (a), and two types of connected dodecahedra in 2 (b). For the sake of clarity, only N, Cl, and O atoms are shown. The topological nets can be assigned to the classes cbs/CrB (chromium boride type) and tcs (thorium chromium silicide type) in the case 1a and 2, respectively.
Figure 7. Topological nets, showing three different kinds of connected strands in 1a (a), and two types of connected dodecahedra in 2 (b). For the sake of clarity, only N, Cl, and O atoms are shown. The topological nets can be assigned to the classes cbs/CrB (chromium boride type) and tcs (thorium chromium silicide type) in the case 1a and 2, respectively.
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Table
Table 1. Crystal data and structure refinement parameters for 1a, 1b, and 2.
Table 1. Crystal data and structure refinement parameters for 1a, 1b, and 2.
Parameters1a1b2
CCDC depository196690418967791966943
Crystal data
Color/shapeColorless/blockColorless/blockColorless/block
Chemical formulaC5H16N2Cl2C5H16N2Cl2C5H18N2OCl2
Mr175.10175.10193.11
Temperature [K]293 (2)293 (2)293 (2)
Wavelength [Å]Mo Kα 0.71073Mo Kα 0.71073Mo Kα 0.71073
Crystal system, space groupMonoclinic, C2/cMonoclinic, CcTriclinic, P 1 ¯
a,
b,
c [Å]		20.7779 (7),
8.2560 (3),
10.9433 (3)		32.1820 (1),
14.9592 (6),
18.7867 (8)		6.2170 (3),
8.2491 (9),
11.2617 (8)
α,
β,
γ [°]		90,
93.800 (3),
90		90,
125.532 (7),
90		108.876 (8),
91.412 (5),
109.706 (7)
Volume [Å3]1873.1 (1)7360.2 (7)508.66 (8)
Z8322
ρcalc. [g·cm−3]1.241.261.26
µ [mm−1]0.630.640.59
Crystal size (mm3)1.09 × 0.76 × 0.531.09 × 0.80 × 0.460.69 × 0.55 × 0.39
Data collection
DiffractometerOxford Xcalibur EosOxford Xcalibur EosOxford Xcalibur Eos
Absorption correctionMulti-scan (CrysAlisPRO)Analytical (CrysAlisPRO)Multi-Scan (CrysAlisPro)
Tmin, Tmax0.800, 1.0000.596, 0.7700.798, 1.000
F0007523008208
θ range for data collection [°]4.53 ≤ θ ≤ 35.114.12 ≤ θ ≤ 27.502.79 ≤ θ ≤ 27.50
Completeness [%]99.499.6100.0
No. of collected reflections15949571697957
No. of independent reflections4000168167957
No. of observed reflections3248150136626
Rint0.0260.0200.039
Refinement
R values [F2 > 2σ(F2)]R1 = 0.032, wR2 = 0.069R1 = 0.030, wR2 = 0.065R1 = 0.043, wR2 = 0.096
R values (all data)R1 = 0.044, wR2 = 0.075R1 = 0.036, wR2 = 0.069R1 = 0.052, wR2 = 0.102
S (Goodness-of-fit)1.041.061.09
No. of data (m)4000168167957
No. of parameters (n)10870399
No. of restraints020
Δρmax, Δρmin0.44, −0.320.30, −0.330.48, −0.50
R1 = Σ∣∣Fo∣ − ∣Fc∣∣ ÷ Σ∣Fo∣; wR2 = [Σ w(Fo2 − Fc2)2 ÷ Σ w(Fo2)2]−1/2; S = [Σ w(Fo2 − Fc2)2 ÷ (m − n)]−1/2; w = 1 ÷ σ2(Fo2) + (aP)2 + bP; P = (Fo2 + 2Fc2) ÷ 3. Weighting factor a for 1a, 1b and 2: 0.02, 0.02, 0.01. Weighting factor b for 1a, 1b and 2: 1.30, 5.00, 0.60. CCDC 1896779, 1966904 and 1966943 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html (accessed on 1 April 2022) (or from the CCDC, 12 Union Road, Cambridge CB2 1EZ, UK; Fax: +44 1223 336033; E-mail: [email protected]).
Table
Table 2. Hydrogen-bond geometry (Å, °) for 1a and 2.
Table 2. Hydrogen-bond geometry (Å, °) for 1a and 2.
D-H∙∙∙AD-HH∙∙∙AD∙∙∙AD-H∙∙∙A
Compound 1a
N1-H11···Cl10.87 (2)2.30 (2)3.1619 (9)170 (2)
N1-H12···Cl20.89 (2)2.35 (2)3.146 (1)148 (1)
N1-H13···Cl1i0.90 (2)2.27 (2)3.163 (1)175 (1)
N2-H21···Cl2iv0.76 (2)2.66 (2)3.183 (1)128 (2)
N2-H22···Cl1ii0.88 (2)2.49 (2)3.272 (1)149 (2)
N2-H23···Cl2iii0.87 (2)2.33 (2)3.180 (1)165 (2)
Compound 2
N1-H11···Cl1i0.892.663.234 (2)122.9
N1-H11···Cl2ii0.892.683.245 (2)122.5
N1-H12···Cl10.892.313.195 (2)174.3
N1-H13···Cl1iii0.892.353.173 (2)153.7
N2-H21···Cl2iv0.892.333.206 (3)169.2
N2-H22···Cl1v0.892.573.223 (2)131.2
N2-H22···Cl2vi0.892.803.318 (3)118.7
N2-H23···Cl20.892.393.189 (2)149.0
O1-H1O···Cl2iv1.052.223.259 (6)175.7
O1-H2O···Cl1vii0.912.223.136 (7)177.6
O2-H3O···O11.091.692.776 (8)177.5
Symmetry codes for 1a: (i) 1/2−x, 1/2−y, 1−z; (ii) 1/2−x, 3/2−y, 1−z; (iii) x, 1−y, z−1/2; (iv) x, 1+y, z. Symmetry codes for 2: (i) 1−x, −y, 1−z; (ii) 1−x, 1−y, 2−z; (iii) −x, −y, 1−z; (iv) 1−x, 2−y, 2−z; (v) 1−x, 1−y, 1−z; (vi) 2−x, 2−y, 2−z; (vii) x, y+1, z; (viii) −x, 1−y, 1−z.
Table
Table 3. Torsion angles (°) and conformations of the (dmpnH2)2+ cation in experimental structures.
Table 3. Torsion angles (°) and conformations of the (dmpnH2)2+ cation in experimental structures.
CompoundΘ1Θ2ConformationReference
C5H16N2Cl2 (1a)169.77 (9)−178.15 (9)aa
C5H16N2Cl2 (1b)−174.0 (4)76.0 (5)ag[19]
54.3 (6)174.5 (4)ga
174.1 (4)49.7 (6)ag
76.4 (5)−174.1 (4)ga
54.1 (7)172.2 (5)ga
74.9 (5)−173.4 (4)ga
72.3 (5)−174.1 (4)ga
52.7 (6)175.6 (4)ga
C5H16N2Cl2·H2O (2)176.8 (2)−171.2 (2)aa
C5H16N2Br2−171.2 (5)177.7 (5)aa[11]
C5H16N2I2−71 (1)−71 (1)gg[11]
C5H16N2I2·I2180.0 (3)180.0 (3)aa[12]
C5H16N2 (NO3)2−58.8 (2)−64.0 (2)gg[13]
C5H16N2 [CrO4]−178.3 (2)−169.0 (2)aa[14]
C5H16N2 [ZnCl4]176.38 (8)165.16 (8)aa[15]
C5H16N2 [CdBr4]74.6 (8)−176.2 (8)ga[16]
(C5H16N2)3 [InBr4] [In2Br11]−170 (1)−177 (1)aa[17]
178.2 (6)74.4 (8)ag
178.4 (6)70.3 (8)ag
Abbreviations for the conformations of the (dmpnH2)2+ cation are used as follows: anti-periplanar (a); gauche (g); anti-clinal (c); rotation of N1C1–C2C3 (Θ1) rotation of C1C2–C3N2 (Θ2).
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Heimgert, J.; Morsbach, F.; Kleinschmidt, M.; Reiss, G.J. Synthesis, Structural Characterization, Conformational and Topological Classification of Different Salts in the 2,2-Dimethylpropane-1,3-diamine/HCl/H2O-System. Solids 2022, 3, 385-396. https://doi.org/10.3390/solids3030027

AMA Style

Heimgert J, Morsbach F, Kleinschmidt M, Reiss GJ. Synthesis, Structural Characterization, Conformational and Topological Classification of Different Salts in the 2,2-Dimethylpropane-1,3-diamine/HCl/H2O-System. Solids. 2022; 3(3):385-396. https://doi.org/10.3390/solids3030027

Chicago/Turabian Style

Heimgert, Jaqueline, Florian Morsbach, Martin Kleinschmidt, and Guido J. Reiss. 2022. "Synthesis, Structural Characterization, Conformational and Topological Classification of Different Salts in the 2,2-Dimethylpropane-1,3-diamine/HCl/H2O-System" Solids 3, no. 3: 385-396. https://doi.org/10.3390/solids3030027

APA Style

Heimgert, J., Morsbach, F., Kleinschmidt, M., & Reiss, G. J. (2022). Synthesis, Structural Characterization, Conformational and Topological Classification of Different Salts in the 2,2-Dimethylpropane-1,3-diamine/HCl/H2O-System. Solids, 3(3), 385-396. https://doi.org/10.3390/solids3030027

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