Self-assembly mechanism based on charge density topological interaction energies

The packing interactions have been evaluated in the context of the self-assembly mechanism of crystal growth and also for its impacts on the aromaticity of the trimesate anion. The structure of ethylammonium trimesate hydrate (1) measured at 100 K and a charge density model, derived in part from theoretical structures, is reported. Theoretical structure factors were obtained from the geometry-optimized periodic wave function. The trimesic acid portion of 1 is fully deprotonated and participates in a variety hydrogen bonding motifs. Topological analysis of the charge density model reveals the most significant packing interactions and is then compared to a complementary analysis performed by the Hirshfeld surface method. The results presented herein demonstrate that in organic salt crystals the small structural motifs are most stable and once formed as stand-alone structures, may direct the self-assembly process. Moreover, when intermolecular interactions supported by the electrostatic forces are analyzed, the care must be taken with interpretation of the results of Hirshfeld surface analysis for organic salts crystals.     

Ligand-induced polyhedral opening in the mixed-metal cluster MeCCo2NiCp(CO)6 by 4,5-Bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd): X-ray structure of Co2NiCp(CO)4[μ2,η2,η1-C(Me)C=C(PPh2)C(O)CH2C(O)](μ2-PPh2)

The mixed-metal cluster MeCCo₂NiCp(CO)₆ (1) reacts with the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) in refluxing CH₂Cl₂ to afford the disubstituted cluster MeCCo₂NiCp(CO)₄(bpcd) (2), which exists as a 1:1 mixture of bridging and chelating bpcd isomers. VT ³¹P NMR spectroscopy confirms that the two bpcd isomers do not interconvert in solution over the temperature range of 182–298 K. Thermolysis of cluster 2 leads to bpcd/cluster activation and formation of the phosphido-bridged cluster Co₂NiCp(CO)₄[μ₂,η²,η¹-C(Me)C=C(PPh₂)C(O)CH₂C(O)](μ₂-PPh₂) (3). The ligand-induced polyhedral expansion that accompanies the formation of the title cluster was established by X-ray diffraction analysis. Co₂NiCp(CO)₄[μ₂,η²,η¹-C(Me)C=C(PPh₂)C(O)CH₂C(O)](μ₂-PPh₂) crystallizes in the triclinic space group P-1, a=9.679(2), b=11.691(2), c=16.653(3) ?, α=85.849(3)°, β=85.456(4)°, γ=66.453(3)°, V=1720.3(6) A³, Z=2, D _cacl=1.632 Mg/m³; R=0.0874, R _w=0.1998 for 7053 observed reflections with I > 2σ(I).     

Structures and nonlinear optical properties of polar 2-amino-1,2,3-triazolequinone derivatives

A series of phenyldialkylamine, dimethoxyphenyl, and nitrothiophene derivatives of 2-amino-1,2,3-triazolequinones was characterized by NMR, IR, mass spectroscopy, cyclic voltammetry, and chemical analyses. The solvatochromic procedure was used to evaluate the potential of nine compounds for nonlinear optical applications, and the possible failure of this model is discussed. The crystal structures of seven compounds were determined: (4) P2₁/c, a = 15.430(3) Å, b = 7.633(2) Å, c = 15.940(3) Å, = 105.19(3)° (5) P2₁/c, a = 20.201(2) Å, b = 9.6579(9) Å , c = 18.517(2) Å, = 95.907(2)° (6) P-1, a = 7.769(2) Å, b = 8.515(3) Å, c = 17.312(5) Å, = 89.347(7)°, = 83.219(6)°, = 86.001(7)° (7) P-1, a = 8.1365(7) Å, b = 8.9605(8) Å, c = 11.630(1) Å, = 79.553(2)°, = 75.048(2)°, = 82.080(2)° (8) P-1, a = 8.298(3) Å, b = 9.720(3) Å, c = 10.033(3) Å, = 84.803(6)°, = 83.735(6)°, = 77.659(5)° (10) P2₁/n, a = 8.4300(7) Å, b = 13.980(1) Å, c = 13.975(1) Å, = 106.590(2)° (12) P2₁/n, a = 7.715(2) Å, b = 14.206(3) Å, c = 12.758(3) Å, = 91.016(5)°.     

Structures and properties of 1,4-dithiins and related molecules

A series of organosulfur compounds was characterized by NMR, IR, mass spectroscopy, cyclic voltammetry, and chemical analyses. The crystal structures of six compounds were determined: 1,3-dithioleno[4,5-e]naphtho[2,3-b]1,4-dithiin-2,5, 10-trione (1b), P , a = 7.665(4), b = 7.997(4), c = 11.443(5) Å, = 91.311(8), = 92.516(8), = 117.53(7)° 6,7-dimethylbenzo[1,2-b]1,3-dithioleno[4,5-e]1,4-dithiin-2,5,8-trione (2b), P2₁/m, a = 3.933(1), b = 12.864(2), c = 11.943(3) Å, = 99.161(4)° 6-phenyl-2-thioxo-6-hydrocyclopenta[2,1-b]1,3-dithioleno[4,5-e]1,4-dithiin-5,7-dione (3a), C2/c, a = 32.408(6), b = 3.8743(8), c = 27.123(5) Å, = 125.171(7)° 6-phenyl-1,3-dithioleno[4,5-e]3-pyrrolino[3,4-b]1,4-dithiin-5,7-trione (3b), P2₁/n, a = 7.9712(9), b = 6.1976(7), c = 55.978(6) Å, = 91.096(1)° 2,3,7,8-tetramethylthianthrene-1,4,6,9-tetraone (4), P2₁/c, a = 4.195(1), b = 17.924(5), c = 9.682(3) Å, = 98.509(5)° 3H,6H-1,4-oxathiino[6,5-2,1]naphtho[3,4-e]1,4-oxathiin-2,7-dione (5), P2₁/n, a = 9.3522(7), b = 7.8782(6), c = 17.118(1) Å, = 93.171(1)°. Several structures exhibited significant S—S intermolecular interactions, suggesting that the molecules might be precursors for preparing nonmetallic conductors.     

trans‐4‐Bromo‐ONN‐azoxy­benzene at 100 K

The crystal structure of the α isomer of trans‐4‐bromo­azoxy­benzene [systematic name: trans‐1‐(bromophenyl)‐2‐phenyl­diazene 2‐oxide], C₁₂H₉BrN₂O, has been determined by X‐ray dif­frac­tion. The geometries of the two mol­ecules in the asymmetric unit are slightly different and are within ∼0.02 Å for bond lengths, ∼2° for angles and ∼3° for torsion angles. The azoxy bridges in both mol­ecules have the typical geometry observed for trans‐azoxy­benzenes. The crystal network contains two types of planar mol­ecules arranged in columns. The torsion angles along the Ar—N bonds are only 7 (2)°, on either side of the azoxy group.     

Phosphorus mononitride: A difficult case for theory

Phosphorus nitride (PN) is the simplest molecule formed solely by phosphorus and nitrogen. It represents an interesting model for materials, where phosphorus is directly attached to nitrogen. Nevertheless, both theoretical and experimental studies often provide an incomplete picture on the structural, electronic, and spectral properties of PN. Theoretical predictions often suffer from insufficient level of theory, incomplete basis set, or from neglecting several effects, for example, zero-point vibrational correction (ZPVC). Therefore, we performed an extensive benchmark study on structural, electronic, and spectral properties of PN at the Hartree-Fock, density functional theory (DFT), or even the coupled-cluster levels. We paid special attention to the basis set effect. We tested three variants of Dunning's aug-cc-pVXZ basis sets with the size from double-ζ to sextuple-ζ, as well as Jensen's aug-pc-n, aug-pcJ-n, and aug-pcSseg-n basis sets, where n = 1-4. Obtained energetics, PN distance, dipole moment, vibrational frequencies, and nuclear magnetic resonance (NMR) parameters were extrapolated to the complete basis set limit (CBS) using three- or two-parameter formulas. The ³¹P NMR shieldings estimated with the aug-cc-pVXZ and aug-cc-pV(X + d)Z basis sets strongly depend on the basis set size providing scattered convergence patterns toward CBS. The Hartree-Fock self-consistent field (HF-SCF) NMR parameters evinced similar behavior as the coupled-cluster data. The only smooth convergence was achieved using the aug-cc-pCVXZ basis sets that include core-valence effects. The KT3 functional underestimated the phosphorus CBS shieldings by about 12 ppm compared to coupled cluster with singles and doubles (CCSD) (T). Nevertheless, KT3 unambiguously surpasses the HF-SCF and CCSD levels that provide ³¹P shieldings that are lower by about 150 ppm and 24 ppm compared to CCSD(T). The convergence of nitrogen shieldings was regular for all basis set hierarchies and all theoretical methods. Relativistic and vibrational effects on selected properties were also discussed.     

Temperature-dependent polymorphism of N-(4-fluorophenyl)-1,5-dimethyl-1H-imidazole-4-carboxamide 3-oxide: experimental and theoretical studies on intermolecular interactions in the crystal state

X-ray analysis of N-(4-fluorophenyl)-1,5-dimethyl-1H-imidazole-4-carboxamide 3-oxide reveals the temperature-dependent polymorphism associated with the crystallographic symmetry conversion. The observed crystal structure transformation corresponds to a symmetry reduction from I4₁ /a (I) to P4₃ (II) space groups. The phase transition mainly concerns the subtle but clearly noticeable reorganization of molecules in the crystal space, with the structure of individual molecules left almost unchanged. The Hirshfeld surface analysis shows that various intermolecular contacts play an important role in the crystal packing, revealing graphically the differences in spatial arrangements of the molecules in both polymorphs. The N-oxide oxygen atom acts as a formally negatively charged hydrogen bonding acceptor in intramolecular hydrogen bond of N–H…O^? type. The combined crystallographic and theoretical DFT methods demonstrate that the observed intramolecular N-oxide N–H…O hydrogen bond should be classified as a very strong charge-assisted and closed-shell non-covalent interaction.