Amitriptylinium picrate: conformational disorder

Unravelling the mechanism of amitriptyline removal from water by natural montmorillonite through batch adsorption, molecular simulation and adsorbent characterization studies

Amitriptyline (AMI) is one of the most common tricyclic antidepressant personal care medications. Due to its environmental persistence and bioaccumulation, release of AMI into the environment via wastewater streams in elevated levels could lead to significant ecological and human health impacts. In this study, the adsorption of AMI by montmorillonite (SWy-2), a naturally abundant smectite clay with sodium ions as the main interlayer cations, was investigated. Maximum AMI adsorption (276 mg/g) occurred at pH 7-8. After adsorption, examination of the adsorbent's X-ray diffraction pattern indicated that interlayer expansion had occurred, where chemical stoichiometry confirmed cation exchange as the principal adsorption mechanism. AMI adsorption reached equilibrium within 4 h, with kinetic data best fitting the pseudo-second order kinetic model (R² = 0.98). AMI adsorption was unaffected by solution pH in the range 2-11, where adsorption was endothermic, and molecular simulations substantiated by Fourier transform infrared spectroscopy and thermogravimetric investigations indicated that the orientation of AMI molecules in the interlayer was via an amine group and a benzene ring. Overall this research shows that SWy-2 has significant potential as a low cost, effective, and geologically derived natural material for AMI removal in wastewater systems.

Crystal structures of N,N-dimethyl-(2-(2,2-diphen-yl)-2-prop-2-yn-yloxy)acet-oxy)ethyl-amine and N,N-dimethyl-(2-(2,2-diphen-yl)-2-prop-2-yn-yl--oxy)acet-oxy)ethyl-ammonium 2,4,6-tri-nitro-phenolate

The N,N-di-methyl-ethylamminium unit in N,N-dimethyl-[2-(2,2-diphen-yl)-2-prop-2-ynyloxyacet-oxy]ethyl-amine, C21H23NO3 (I), is disordered over two sets of atomic sites having occupancies of 0.880 (3) and 0. 120 (3), but there are no direction-specific inter-actions between the mol-ecules of (I). The cation in N,N-dimethyl-[2-(2,2-diphen-yl)-2-prop-2-ynyloxyacet-oxy]ethyl-ammonium 2,4,6-tri-nitro-phenolate (picrate), C21H24NO3+·C6H2N3O7- (II), shows a similar type of disorder, with occupancies of 0.654 (11) and 0.346 (11), although the overall conformation of the cation in (II) is different from that in the neutral (I). The component ions are are linked by an almost planar three-centre N-H⋯(O)2 hydrogen bond, and the ion pairs are further linked by a combination of three C-H⋯O hydrogen bonds to form sheets. Comparisons are made with some related structures.

Amitriptyline removal using palygorskite clay

With the increased detections of commonly used pharmaceuticals in surface water and wastewater, extensive attentions were paid recently to the fate and transport of these pharmaceuticals in the environment. Amitriptyline (AMI) is a tricyclic antidepressant widely applied to treat patients with anxiety and depression. In this study, the removal of AMI with palygorskite clay (PFl-1) was investigated under different physico-chemical conditions and supplemented by instrumental analyses. The uptake of AMI on PFl-1 was well fitted by the Langmuir isotherm with an adsorption capacity of 0.168 mmol g(-1) at pH 6-7. The AMI uptake was fast and reached equilibrium in 15 min. The X-ray diffraction patterns showed no shift of the (110) peak position of palygorskite after AMI uptake. However, the (001) peak position of the minor component smectite (about 10%) shifted to lower angle as the amounts of AMI input increased. These results suggested surface uptake of AMI on palygorskite and interlayer uptake of AMI in smectite. As smectite is a common component of palygorskite clays, its role in assessing the properties and performances of palygorskite clays for the uptake and removal of contaminants should not be neglected. Overall, the high affinity of AMI for PFl-1 and strong retention of AMI on PFl-1 suggested that it could be a good adsorbent to remove AMI from wastewater. Palygorskite clays can also be a sink for many cationic pharmaceuticals in the environmental of the arid regions.

Mechanism of amitriptyline adsorption on Ca-montmorillonite (SAz-2)

The uptake of amitriptyline (AMI) from aqueous environment by Ca-montmorillonite (SAz-2) was studied in a batch system under different physicochemical conditions. The adsorbent was characterized by X-ray diffraction and Fourier transform infrared (FTIR) analyses. The AMI adsorption on SAz-2 obeyed the Langmuir isotherm with a capacity of 330mg/g (1.05mmol/g) at pH 6-7. The adsorption kinetics was fast, almost reaching equilibrium in 2h, and followed a pseudo-second-order kinetic model. Desorption of exchangeable cations correlated with the AMI adsorption well, indicating that cation exchange was the major mechanism. X-ray diffraction patterns showing significant expansions of the d001 spacing and characteristic FTIR band shifts toward higher frequencies after AMI adsorption onto SAz-2 indicated that the adsorbed AMI molecules were intercalated into the interlayers of the mineral. Thermodynamic parameters based on partitioning coefficients suggested that the AMI adsorption was an endothermic physisorption at high adsorption levels. At low and higher AMI adsorption levels, the intercalated AMI molecules take a horizontal monolayer and bilayer conformation, respectively. The higher adsorption capacity suggested that SAz-2 could be a good candidate to remove AMI from wastewater and would be an important environmental sink for the fate and transport of AMI in soils and groundwater.

[3-(5-Hy-droxy-5H-dibenzo[a,d]cyclo-hepten-5-yl)prop-yl]dimethyl-ammonium 3-carboxyprop-2-enoate

In the cation of the title salt, C(20)H(24)NO(+)·C(4)H(3)O(4) (-), the N atom in the dimethyl-ammonium group is protonated. The dihedral angle between the mean planes of the two six-membered rings fused to the cyclo-hepten-5-yl ring is 54.4 (1)°. An intra-molecular O-H⋯O hydrogen bond occurs in the anion. The crystal packing is stabilized by inter-molecular O-H⋯O and N-H⋯(O,O) hydrogen bonds and weak C-H⋯O inter-actions, forming a two-dimensional network.

Cyclobenzaprinium chloride

In the title mol­ecular salt [systematic name: 3-(5H-dibenzo[a,d]cyclo­hepten-5-yl­idene)-N,N-dimethyl­propan­aminium chloride], C₂₀H₂₂N⁺·Cl⁻, two cation–anion pairs make up the asymmetric unit. The dihedral angles between the mean planes of the two fused benzene rings of the cation are 49.5 (1) and 50.9 (1)°. The cystal packing is stabilized by N—H⋯Cl hydrogen bonds and weak C—H⋯Cl inter­actions.

Cyclo-benzaprinium salicylate

In the title mol-ecular salt [systematic name: 3-(5H-di-benzo[a,d]cyclo-hepten-5-yl-idene)-N,N-dimethyl-1-propanaminium 2-hy-droxy-benzoate], C(20)H(22)N(+)·C(7)H(5)O(3) (-), the benzene rings of the cyclo-benzaprinium cation are inclined with a dihedral angle of 61.66 (7)°. An intra-molecular O-H⋯O hydrogen bond occurs within the salicylate anion, generating an S(6) ring. In the crystal, the cation and anion are linked by an N-H⋯O inter-action.

Opipramol dipicrate

In the crystal structure of the title compound, C(23)H(31)N(3)O(2+)·2C(6)H(2)N(3)O(7) (-), {systematic name: 1-[3-(5H-dibenz[b,f]azepin-5-yl)prop-yl]-4-(2-hy-droxy-eth-yl)piperazine-1,4-diium bis-(2,4,6-trinitro-phrenolate)} the piperazine group in the opipramol dication is protonated at both N atoms. Each picrate anion inter-acts with the protonated N atom in the cation through a bifurcated N-H⋯O hydrogen bond, forming an R(2) (1)(6) ring motif. In the cation, the dihedral angle between the mean planes of the two benzene rings is 50.81 (8) Å. Inter-molecular O-H⋯O and weak C-H⋯O hydrogen bonds, and weak π-ring and π-π stacking inter-actions dominate the crystal packing.

Desipramine hydro-chloride: a non-merohedrally twinned structure

The title compound, C(18)H(23)N(2) (+)·Cl(-), is a non-merohedrally twinned salt [domains 0.9288 (3) and 0.0712 (3)] which crystallizes with four independent cation-anion pairs in the asymmetric unit. The seven-membered ring in each of the cations adopts a boat conformation, thus creating a butterfly effect within the ring system. The average value of the dihedral angle between the two aromatic rings in the four cations is 57.1 (1)°. The crystal packing is stabilized only slightly by a collection of inter-mediate N-H⋯Cl hydrogen-bonding inter-actions, which produce a weak, but cooperative, infinite, one-dimensional, inter-molecular hydrogen-bond network along the a axis. A MOPAC PM3 computational calculation gives support to these observations.

Trimipraminium maleate

The title compound [systematic name: 3-(10,11-dihydro-5H-dibenzo[b,f]azepin-5-yl)-N,N,2-trimethyl­propan-1-aminium hydrogen maleate], C₂₀H₂₇N₂⁺·C₄H₃O₄⁻, a maleate salt of trimipramine, crystallizes with four independent cation–anion pairs in the asymmetric unit. The trimipramine cation contains a seven-membered azepine ring with two fused benzene rings whose mean planes are separated by 51.7 (1)°. Inter­molecular N—H⋯O and intra­molecular O—H⋯O hydrogen bonds pack the ions into chains along [101]. Additional weak inter­molecular C—H⋯O inter­actions help to influence the twist angles of the mean planes of the benzene rings fused to the azepine ring in the cation. A geometry-optimized MOPAC AM1 theoretical calculation supports these observations.

Imatinibium dipicrate

IN THE CRYSTAL STRUCTURE OF IMATINIBIUM DIPICRATE [SYSTEMATIC NAME: 1-methyl-4-(4-{4-methyl-3-[4-(3-pyrid-yl)pyrimidin-2-yl-amino]-anilinocarbon-yl}benz-yl)piperazine-1,4-diium dipicrate], C(29)H(33)N(7)O(2+)·2C(6)H(2)N(3)O(7) (-), the imatinibium cation is proton-ated at both of the pyrimidine N atoms. Each of the two picrate anions inter-acts with the diprotonated cation through bifurcated N-H⋯O hydrogen bonds forming R(1) (2)(6) ring motifs. Also, an R(2) (2)(24) graph set is formed between the benzamidium -NH- group and the 4-pyridyl N atom inter-acting through N-H⋯N hydrogen-bond inter-actions. Additional weak C-H⋯Cg π-ring and π-π inter-molecular inter-actions are observed which also influence crystal packing.

Chlorimipraminium picrate

The title compound {systematic name: 3-chloro-5-[3-(dimethyl­amino)prop­yl]-10,11-dihydro-5H-dibenz[b,f]azepinium picrate}, C₁₉H₂₄ClN₂⁺·C₆H₂N₃O₇⁻, crystallizes with two independent cation–anion pairs in the asymmetric unit. The chlorimipraminium cation contains two benzene rings (one with a chloro substituent) fused to a V-shaped seven-membered azepine ring whose mean planes are separated by 61.1 (0) and 66.5 (8)° with a 3-(dimethyl­amino)propyl group extending away from the apex of this ring. In the picrate anion, the mean planes of the two o-NO₂ groups in each anion are twisted by 3.7 (2)/31.9 (3) and 31.3 (1)/11.4 (0)°, respectively, with respect to the mean plane of the six-membered benzene ring. The phenolate O atoms are bent slightly away from the mean plane of the benzene ring. The mean planes of the p-NO₂ groups are twisted by 6.6 (1) and 2.88°, respectively, from the mean plane of the benzene ring. The crystal packing features bifurcated N—H⋯(O,O) inter­molecular hydrogen-bond inter­action, which connects each cation–anion pair. Additional π–π ring and C—H⋯π weak inter­molecular inter­actions are also observed.

Propiverinium picrate

THE TITLE COMPOUND [SYSTEMATIC NAME: 4-(2,2-diphenyl-2-prop-oxyacet-oxy)-1-methyl-piperidin-1-ium picrate], C(23)H(30)NO(3) (+)·C(6)H(2)N(3)O(7) (-), crystallizes as a salt with one cation-anion (propiverinium picrate) pair in the asymmetric unit. A significant number of conformational changes are observed between the crystalline environment of this cation-anion salt and that of a density functional theory (DFT) calculation of the geometry-optimized structure. The angle between the dihedral planes of the two benzyl rings in the propiverinium cation increases by 14.4 (0)° from that of the crystalline environment. The dihedral angles between the mean planes of each of the benzyl rings and the mean plane of the piperidine increase by 2.0 (8) and 12.3 (5)°. The angles between the mean plane of the acetate group and the mean planes of the inter-connected piperidine group and the two benzyl rings decrease by 0.2 (1), 7.4 (6) and 3.2 (2)°, respectively. The mean plane of the phenolate group in the anion changes by +22.6 (9), +22.1 (1) and -2.8 (6)° from the mean planes of the piperidine and benzyl rings in the cation, respectively. In the crystal, a bifurcated N-H⋯(O,O) hydrogen bond and a weak C-H⋯π ring inter-action help to establish the packing. The two O atoms of the p-NO(2) group are disordered with occupancies 0.825 (10):0.175 (10).

4-(4-Carboxybenzyl)-1-methylpiperazin-1-ium picrate

The title compound, C₁₃H₁₉N₂O₂⁺·C₆H₂N₃O₇⁻, is a salt obtained by cocrystallization of 4-[(4-methyl­piperazin-1-yl)meth­yl]benzoic acid and picric acid. The cations adopt an ‘L-shaped’ conformation and are linked into chains along [010] by O—H⋯N hydrogen bonds. The NH group of each piperazinium ring forms a hydrogen bond to the phenolate O atom of a picrate anion, and the picrate anions form face-to-face contacts with an inter­planar separation of 3.023 (1) Å.