A fluorescent aptasensor for quantification of cocaine mediated by signal amplification characteristics of UiO-66/AuNPs nanocomposite

Due to the detrimental effects of cocaine on the human body such as organ damage, paranoia, immunodeficiency, cardiovascular disease, blood pressure, and stress, it is highly required to develop sensing approaches for its rapid and facile determination. Based on the signal enhancement capability of the UiO-66/AuNPs nanocomposite and acting as a capture agent, we designed a cost-effective fluorescent aptasensor for cocaine detection. The cocaine presence in the sample would cause a considerable escalation in the quenching of the fluorescence signal. The aptasensor achieved the linear response range over 0.5 μM-20 μM with a low detection limit of 0.178 μM. The selectivity of the designed aptasensing assay was successfully confirmed by examining several analgesic drugs. The aptasensor was employed for cocaine determination in human serum as the real samples. This method has a substantial benefit the for development of a low-cost and facile tool in medicine and forensic science.

Crystal structure of (tricyclohexylphosphane-κP)-[(Z)-N-(3-fluorophenyl)-O-methylthiocarbamato-k1 S]gold(I), C26H40AuFNOPS

C26H40AuFNOPS, triclinic, P1 (no. 1), a = 9.62498(7) Å, b = 11.78239(10) Å, c = 12.74349(13) Å, α = 78.7411(8)°, β = 73.5635(8)°, γ = 76.6096(1)°, V = 1335.34(2) Å3, Z = 2, R gt (F) = 0.0224, wR ref (F 2) = 0.0557, T = 100 K.

Crystal structure of (μ2-1,1′-bis(diphenylphosphino)hexane-κ2 P,P′)-bis[(Z)-N-(3-fluorophenyl)-O-methylthiocarbamato-κS]digold(I), C46H46Au2F2N2O2P2S2

C46H46Au2F2N2O2P2S2, triclinic, P1̄ (no. 2), a = 8.2496(3) Å, b = 11.4366(4) Å, c = 12.9504(4) Å, α = 109.171(3)°, β = 92.496(3)°, γ = 100.208(3)°, V = 1128.98(7) Å3, Z = 1, R gt(F) = 0.0246, wR ref(F 2) = 0.0560, T = 100(2) K.

Crystal structure of (μ2-1,1′-bis(diphenylphosphino)butane-κ2 P,P′)-bis[(Z)-N-(3-fluorophenyl)-O-methylthiocarbamato-κS]-di-gold(I), C44H42Au2F2N2O2P2S2

C44H42Au2F2N2O2P2S2, triclinic, P1̄ (no. 2), a = 8.8035(2) Å, b = 11.4764(3) Å, c = 21.2293(6) Å, α = 83.550(2)°, β = 82.256(2)°, γ = 83.793(2)°, V = 2102.40(10) Å3, Z = 2, R gt(F) = 0.0268, wR ref(F 2) = 0.0577, T = 100(2) K.

[(Z)-N-(3-Fluoro-phen-yl)-O-methyl-thio-carbamato-κS](tri-phenyl-phosphane-κP)gold(I): crystal structure, Hirshfeld surface analysis and computational study

The title phosphanegold(I) thiol-ate, C26H22AuFNOPS or [Au(C8H7FNOS)(C18H15P)], has the AuI centre coordinated by phosphane-P [2.2494 (8) Å] and thiol-ate-S [2.3007 (8) Å] atoms to define a close to linear geometry [P-Au-S = 176.10 (3)°]. The thiol-ate ligand is orientated so that the meth-oxy-O atom is directed towards the Au atom, forming an Au⋯O close contact of 2.986 (2) Å. In the crystal, a variety of inter-molecular contacts are discerned with fluoro-benzene-C-H⋯O(meth-oxy) and phenyl-C-H⋯F inter-actions leading to dimeric aggregates. These are assembled into a three-dimensional architecture by phenyl-C-H⋯S(thiol-ate) and phenyl-C-H⋯π(fluorobenzene, phen-yl) inter-actions. Accordingly, the analysis of the calculated Hirshfeld surface shows 30.8% of all contacts are of the type C⋯H/H⋯C but this is less than the H⋯H contacts, at 44.9%. Other significant contributions to the surface come from H⋯F/F⋯H [8.1%], H⋯S/S⋯H [6.9%] and H⋯O/O⋯H [3.2%] contacts. Two major stabilization energies have contributions from the phenyl-C-H⋯π(fluoro-benzene) and fluoro-benzene-C-H⋯C(imine) inter-actions (-37.2 kcal mol-1), and from the fluoro-benzene-C-H⋯F and phenyl-C-H⋯O inter-actions (-34.9 kcal mol-1), the latter leading to the dimeric aggregate.

Crystal structure of [O-ethyl N-(4-nitrophenyl)thiocarbamato-κS](tri-4-tolylphosphine-κP)gold(I) tetrahydrofuran solvate, C30H30AuN2O3PS, C4H8O

C34H38AuN2O4PS, triclinic, P1̄ (no. 2), a = 10.2034(8) Å, b = 11.5755(9) Å, c = 15.7533(12) Å, α = 69.948(2)°, β = 86.496(2)°, γ = 71.370(2)°, V = 1653.8(2) Å3, Z = 2, R gt(F) = 0.0355, wR ref(F 2) = 0.0858, T = 223(2) K.

Crystal structure of [(Z)-O-isopropyl N-(4-nitrophenyl)thiocarbamato-κS]-(triphenylphosphine-κP)-gold(I), C28H26AuN2O3PS

C28H26AuN2O3PS, triclinic, P1̄ (no. 2), a = 8.6339(3) Å, b = 11.0503(3) Å, c = 14.5091(5) Å, α = 95.615(2)°, β = 105.606(3)°, γ = 94.009(2)°, V = 1320.14(8) Å3, Z = 2, R gt(F) = 0.0332, wR ref(F 2) = 0.0886, T = 100 K.

[O-Isopropyl-N-(4-nitrophenyl)thiocarbamato-κS]-(tri-4-tolylphosphine-κP)gold(I)

The synthesis, spectroscopic characterization and X-ray crystal structure of the title compound, (4-tolyl)3PAu[SC(O-i-Pr)=NC6H4NO2-4] (1) are described. Spectroscopy exhibited the expected features confirming the formation of the compound. The molecular structure of 1 confirms the expected linear P–Au–S coordination geometry defined by thiolate-S and phosphane-P atoms. The nearly 7° deviation from linearity is ascribed to the close approach of the imine-bound phenyl group, indicative of a semi-localized Au…π(arene) interaction. The three-dimensional molecular packing is consolidated by methyl- and tolyl-C–H…O(nitro) and tolyl-C–H…π(tolyl) interactions.

N-(4-Bromophenyl)methoxycarbothioamide

The synthesis, spectroscopic and crystallographic characterisation of the title compound, O-methyl-N-4-bromophenyl thiocarbamate, MeOC(=S)N(H)PhBr-4 (1), are described. Spectroscopy confirmed the formation of the compound and the molecular structure was determined crystallographically. Two independent but chemically similar molecules comprise the asymmetric unit of 1. The C‒S and C‒N bond lengths confirm the presence of the thioamide tautomer. The thione-S and amide-N‒H atoms are syn, enabling the formation of amide-N‒H…S(thione) hydrogen bonds between the two independent molecules that generates a two-molecule aggregate via an eight-membered {…HNCS}2 synthon. The aggregates are connected into a three-dimensional architecture via weak intermolecular interactions, including Br…π(4-bromophenyl), S…π(4-bromophenyl), and weak Br…S halogen bonding contacts. The overall molecular conformation, thioamide tautomer, and the presence of amide-N‒H…S(thione) hydrogen bonding in the crystal conform with expectation for this class of compound.

New monoclinic form of {O-Ethyl N-(4-nitro-phen-yl)thio-carbamato-κS}(tri-4-tolyl-phosphane-κP)gold(I): crystal structure and Hirshfeld surface analysis

The title phosphanegold(I) thiol-ate compound, [Au(C9H9N2O3S)(C21H21P)], is a second monoclinic polymorph (space group P21/c) that complements a previously reported Cc polymorph [Broker & Tiekink (2008 ▸). Acta Cryst. E64, m1582]. An SP donor set defines an approximately linear geometry about the gold atom in both forms. The key distinguishing feature between the present structure and the previously reported polymorph rests with the relative disposition of the thiol-ate ligand. In the title compound, the orientation is such to place the oxygen atom in close contact with the gold atom [Au⋯O = 2.915 (2) Å], in contrast to the aryl ring in the original polymorph. In the crystal, linear supra-molecular chains along the a-axis direction mediated by C-H⋯π and nitro-O⋯π inter-actions are found. These pack with no directional inter-actions between them. The analysis of the Hirshfeld surfaces for both forms of [Au(C9H9N3O3S)(C21H21P)] indicates quite distinctive inter-action profiles relating to the differences in inter-molecular contacts found in their respective crystals.

A non-solvated form of [(Z)-O-methyl-N-(2-methyl-phen-yl)-thio-carbamato-κS](tri-phenyl-phosphane-κP)gold(I): crystal structure and Hirshfeld surface analysis

The title compound, [Au(C9H10NOS)(C18H15P)], features a near linear P-Au-S arrangement defined by phosphane P and thiol-ate S atoms with the minor distortion from the ideal [P-Au-S is 177.61 (2)°] being traced in part to the close intra-molecular approach of an O atom [Au⋯O = 3.040 (2) Å]. The packing features supra-molecular layers lying parallel to (011) sustained by a combination of C-H⋯π and π-π [inter-centroid distance = 3.8033 (17) Å] inter-actions. The mol-ecular structure and packing are compared with those determined for a previously reported hemi-methanol solvate [Kuan et al. (2008 ▸). CrystEngComm, 10, 548-564]. Relatively minor differences are noted in the conformations of the rings in the Au-containing mol-ecules. A Hirshfeld surface analysis confirms the similarity in the packing with the most notable differences relating to the formation of C-H⋯S contacts between the constituents of the solvate.

A conformational polymorph of Ph3PAu[SC(OEt)=NPh] featuring an intramolecular Au···π interaction

A conformational polymorph, form β, for Ph3PAu[SC(OEt)=NPh] has been characterised. Like the original structure (form α), the molecule features a linear P–Au–S geometry. The difference between molecular structures rests with the relative disposition of the thiolate ligand which places the N-bound aryl ring in close proximity to the gold centre (form β) rather than the oxygen atom (form α). Density functional theory calculations show the molecule with the Au···π interaction is more stable by 5.2 kcal/mol than the one with the Au···O contact. The molecular packing of both forms are stabilised by C–H···O and C–H···π interactions which make approximately the same contribution to the overall Hirshfeld surfaces. However, key indicators, e.g. crystal packing efficiency and density, and the computational results suggest form β is the thermodynamically favoured form.

A monoclinic polymorph of [(Z)-N-(3-chloro-phen-yl)-O-methyl-thio-carbamato-κS](tri-phenyl-phosphane-κP)gold(I): crystal structure and Hirshfeld surface analysis

The title compound, [Au(C8H7ClNOS)(C18H15P)], is a monoclinic (P21/n, Z' = 1; form β) polymorph of the previously reported triclinic form (P-1, Z' = 1; form α) [Tadbuppa & Tiekink (2010 ▸). Acta Cryst. E66, m664]. The mol-ecular structures of both forms feature an almost linear gold(I) coordination geometry [P-Au-S = 175.62 (5)° in the title polymorph], being coordinated by thiol-ate S and phosphane P atoms, a Z conformation about the C=N bond and an intra-molecular Au⋯O contact. The major conformational difference relates to the relative orientations of the residues about the Au-S bond: the P-Au-S-C torsion angles are -8.4 (7) and 106.2 (7)° in forms α and β, respectively. The mol-ecular packing of form β features centrosymmetric aggregates sustained by aryl-C-H⋯O inter-actions, which are connected into a three-dimensional network by aryl-C-H⋯π contacts. The Hirshfeld analysis of forms α and β shows many similarities with the notable exception of the influence of C-H⋯O inter-actions in form β.

Crystal structures of 5-amino-N-phenyl-3H-1,2,4-di-thia-zol-3-iminium chloride and 5-amino-N-(4-chloro-phen-yl)-3H-1,2,4-di-thia-zol-3-iminium chloride monohydrate

The crystal and mol-ecular structures of the title salt, C8H8N3S2 (+)·Cl(-), (I), and salt hydrate, C8H7ClN3S2 (+)·Cl(-)·H2O, (II), are described. The heterocyclic ring in (I) is statistically planar and forms a dihedral angle of 9.05 (12)° with the pendant phenyl ring. The comparable angle in (II) is 15.60 (12)°, indicating a greater twist in this cation. An evaluation of the bond lengths in the H2N-C-N-C-N sequence of each cation indicates significant delocalization of π-electron density over these atoms. The common feature of the crystal packing in (I) and (II) is the formation of charge-assisted amino-N-H⋯Cl(-) hydrogen bonds, leading to helical chains in (I) and zigzag chains in (II). In (I), these are linked by chains mediated by charge-assisted iminium-N(+)-H⋯Cl(-) hydrogen bonds into a three-dimensional architecture. In (II), the chains are linked into a layer by charge-assisted water-O-H⋯Cl(-) and water-O-H⋯O(water) hydrogen bonds with charge-assisted iminium-N(+)-H⋯O(water) hydrogen bonds providing the connections between the layers to generate the three-dimensional packing. In (II), the chloride anion and water mol-ecules are resolved into two proximate sites with the major component being present with a site occupancy factor of 0.9327 (18).

Crystal structure of 1-(4-methyl-phen-yl)-3-(propan-2-yl-idene-amino)-thio-urea

In the title thio-semicarbazone, C11H15N3S, the p-tolyl-N-H and imino-N-H groups are anti and syn, respectively, to the central thione-S atom. This allows for the formation of an intra-molecular p-tolyl-N-H⋯N(imino) hydrogen bond. The mol-ecule is twisted with the dihedral angle between the p-tolyl ring and the non-hydrogen atoms of the N=CMe2 residue being 29.27 (8)°. The crystal packing features supra-molecular layers lying in the bc plane whereby centrosymmetric aggregates sustained by eight-membered thio-amide {⋯HNCS}2 synthons are linked by further N-H⋯S hydrogen bonds. Layers are connected via methyl-C-H⋯π inter-actions. The supra-molecular aggregation was further investigated by an analysis of the Hirshfeld surface and comparison made to related structures.

Crystal structure of bis-[μ-bis-(di-phenyl-phosphanyl)methane-κ(2) P:P']digold(I) dichloride acetone monosolvate monohydrate

In the title complex salt, [Au2{(C6H5)2PCH2P(C6H5)2}]Cl2·(CH3)2C=O·H2O, the dication forms an eight-membered {-PCPAu}2 ring with a transannular aurophilic inter-action [Au⋯Au = 2.9743 (2) Å]. The ring approximates a flattened boat conformation, with the two methyl-ene C atoms lying ca 0.58-0.59 Å above the least-squares plane defined by the Au2P4 atoms (r.m.s. deviation = 0.0849 Å). One Cl(-) anion functions as a weak bridge between the Au(I) atoms [Au⋯Cl = 2.9492 (13) and 2.9776 (12) Å]. The second Cl(-) anion forms two (water)O-H⋯Cl hydrogen bonds about a centre of inversion, forming a centrosymmetric eight-membered {⋯HOH⋯Cl}2 supra-molecular square. Globally, the dications and loosely associated Cl(-) anions assemble into layers lying parallel to the ac plane, being connected by C-H⋯Cl,π(phen-yl) inter-actions. The supra-molecular squares and solvent acetone mol-ecules are sandwiched in the inter-layer region, being connected to the layers on either side by C-H⋯Cl,O(acetone) inter-actions.