Crystal structure determination

During the systematic investigation of the ternary system Ca(CH3COO)2-Ca(HCOO)2-H2O at room temperature, the congruent crystallisation of two solid calcium acetate formates was observed: the hitherto unknown Ca3(CH3COO)4(HCOO)2·4H2O and the poorly...

The asymmetric unit of the compound I, [Cu II (tetren)](NO3)2, contains one [Cu(tetren)] 2+ cation (tetren is Tetraethylenepentammine) and two nitrate. In the cation, Cu 2+ ion is coordinated by four N atoms from Tetraethylenepentammine and two nitrate ligands in distorted octahedral geometry. In the crystal, the components are linked via N-H...O hydrogen bonds, forming sheets lying parallel to (001). The Metal complex [Cu II (tn)2(No3)2], the Cu II atom has a distorted octahedral coordination sphere and is coordinated by N atoms of two 1,3-diaminiopropane and two nitrate ligands in the equatorial plane. The asymmetric unit is completed, which are involved in hydrogen bonding with N-H functionalities of the free nitrate groups. The crystal structure also features N-H...O hydrogen bonds formed by the NH2 groups, forming sheets and ribbon lysing parallel to (001) for compound II. Anti-bacterial study reveals that complexes are better anti-microbial agents than three Schiff base due to bacterial cell penetration by chelation.

Using direct methods starting from random phases, the crystal structure of a 32-base-pair RNA (675 non-H RNA atoms in the asymmetric unit) was determined using only the native diffraction data (resolution limit 1.05 A ˚) and the computer program SIR2014. The almost three helical turns of the RNA in the asymmetric unit introduced partial or imperfect translational pseudosymmetry (TPS) that modulated the intensities when averaged by the l Miller indices but still escaped automated detection. Almost six times as many random phase sets had to be tested on average to reach a correct structure compared with a similar-sized RNA hairpin (27 nucleotides, 580 non-H RNA atoms) without TPS. More sensitive methods are needed for the automated detection of partial TPS.

LASSBio-1289 compound has been found to promote intense vasodilation and antihypertensive activity. It is an innovative compound, without structural similarities to the three main classes of calcium antagonists IJ1,4-dihydropyridines, benzothiazepines and phenylalkylamines) commonly used. A complete knowledge of the structure, including stereochemistry, is essential to lead optimization in drug discovery. For this reason, in this work we determined the crystal structure of this novel vasoactive N-methyl-N-acylhydrazone derivative by means of X-ray powder diffraction data and an ab initio simulating annealing approach, allowing us to observe the relative configuration E of the imine double bond and its conformation as well as its most relevant intermolecular interactions. These findings were also checked by a FTIR analysis and confirmed in solution by NMR. The compound crystallized under a monoclinic crystal system with space group P2 1 /c and unit cell parameters a = 14.5118(3) Å, b = 12.1374(2) Å, c = 7.5498(1) Å, β = 91.113(1)°, V = 1329.53(4) Å 3 , Z = 4, Z′ = 1 and ρ calc = 1.44042(4) g cm −3. Moreover, a crystal morphology prediction, experimentally compared with SEM inferred images, allowed a direct comparison of the microcrystalline habit and quality, allowing a study of the potential solvent effect on the crystal growth.

Many N-acylhydrazone derivatives synthetized in LASSBio® cannot be prepared as single crystals of sufficient size and/or quality for structure determination to be carried out using single crystal X-ray diffraction techniques. This article highlights the opportunity for determining crystal structures of this class of compounds directly from powder diffraction data. For this task, the crystal structure of LASSBio-294 was re-determined by means of conventional X-ray powder diffraction data and so, compared with the crystal structure already determined for single crystal data. LASSBio-294 is a cardioactive compound of the N-acylhydrazone class, which can become part of the therapeutic interventions designed to decrease exertional fatigue, and, consequently, improve the quality of life of patients suffering from chronic heart failure. Its final crystal structure was refined by means of the Rietveld method (Rietveld, 1967; 1969). This drug crystallizes in a monoclinic (P21/c) space group, with unit cell parameters a = 11.3413(3) Å, b = 12.3573(4) Å, c = 9.0158(3) Å, β = 89.821(2)°, V = 1263.55(7) Å3, Z = 4, Z ́ = 1 and calc = 1.4419(1) g cm-3. The goodness-of-fit indicator and R-factors were, respectively: χ2 = 1.203, RBragg = 0.696%, Rwp = 5.59%, Rexp = 4.65% and Rp = 4.18%. The molecules in LASSBio-294 are H-bonded along the c-axis involving the atoms N(3)–H(8)···O(4).

ABSTRACT LASSBio-1289 compound has been found to promote intense vasodilation and antihypertensive activity. It is an innovative compound, without structural similarities to the three main classes of calcium antagonists (1,4-dihydropyridines, benzothiazepines and phenylalkylamines) commonly used. A complete knowledge of the structure, including stereochemistry, is essential to lead optimization in drug discovery. For this reason, in this work we determined the crystal structure of this novel vasoactive N-methyl-N-acylhydrazone derivative by means of X-ray powder diffraction data and an ab initio simulating annealing approach, allowing us to observe the relative configuration E of the imine double bond and its conformation as well as its most relevant intermolecular interactions. These findings were also checked by a FTIR analysis and confirmed in solution by NMR. The compound crystallized under a monoclinic crystal system with space group P21/c and unit cell parameters a = 14.5118(3) Å, b = 12.1374(2) Å, c = 7.5498(1) Å, β = 91.113(1)°, V = 1329.53(4) Å 3 , Z = 4, = 1 and ρcalc = 1.44042(4) g cm -3 . Moreover, a crystal morphology prediction, experimentally compared with SEM inferred images, allowed a direct comparison of the microcrystalline habit and quality, allowing a study of the potential solvent effect on the crystal growth.

During the systematic investigation of the ternary system Ca(CH 3 COO) 2-Ca(HCOO) 2-H 2 O at room temperature, the congruent crystallisation of two solid calcium acetate formates was observed: the hitherto unknown Ca 3 (CH 3 COO) 4 (HCOO) 2 ·4H 2 O and the poorly characterised Ca(CH 3 COO) (HCOO)·H 2 O. The latter is a frequently observed efflorescence phase found on calcareous objects and it could be also identified as a corrosion phase in a natural history collection of birds' eggs. Elemental and thermal analyses were employed to determine the phase compositions and by Raman and IR spec-troscopy the presence of acetate and formate anions in both solids was confirmed. Laboratory X-ray powder diffraction data were used to solve the crystal structures. Ca 3 (CH 3 COO) 4 (HCOO) 2 ·4H 2 O crystal-lises in a primitive tetragonal unit cell with space group P4 1 2 1 2 and lattice parameters of a = 6.8655(1) Å and c = 45.5454(6) Å, while Ca(CH 3 COO)(HCOO)·H 2 O crystallises in a primitive monoclinic unit cell with space group P2 1 /c and lattice parameters of a = 9.2729(1) Å, b = 6.8002(1) Å, c = 11.2219(2) Å and β = 121.232(1)°. Calcium carboxylate zigzag chains [Ca(µ 2-RCOO) + ] n (R = CH 3 or H) are the main motif of both crystal structures. In Ca 3 (CH 3 COO) 4 (HCOO) 2 ·4H 2 O these chains are exclusively composed of acetate anions, whereas in Ca(CH 3 COO)(HCOO)·H 2 O only formate anions are situated in the chains. The remaining places in the 7-8 fold coordination sphere of the calcium cations are filled by water molecules and additional carboxylate anions that interconnect neighbouring chains, which eventually leads to layered motifs in both structures.

Many N-acylhydrazone derivatives synthetized in LASSBio ® cannot be prepared as single crystals of sufficient size and/or quality for structure determination to be carried out using single crystal X-ray diffraction techniques. This article highlights the opportunity for determining crystal structures of this class of compounds directly from powder diffraction data.

Many N-acylhydrazone derivatives synthetized in LASSBio ® cannot be prepared as single crystals of sufficient size and/or quality for structure determination to be carried out using single crystal X-ray diffraction techniques. This article highlights the opportunity for determining crystal structures of this class of compounds directly from powder diffraction data.