Radiolabeled florescent-magnetic graphene oxide nanosheets: probing the biodistribution of a potential PET-MRI hybrid imaging agent for detection of fibrosarcoma tumor

PURPOSE

Radiolabeled graphene oxide (GO) nanosheets has been one of the most extensively studied nanoplatform for in vivo radioisotope delivery. Herein, we describe the functionalization of the surface of GO nanosheets with Fe3O4 magnetic nanoparticles, cysteine amino acid as an interface ligand, and cadmium telluride quantum dots.

MATERIALS AND METHODS

To enable In vivo PET imaging, the GO@Fe3O4-cys-CdTe QDs were labeled with 68Ga to yield [68Ga] Ga-Go@ Fe3O4-Cys-CdTe QDs. Furthermore, serum stability tests were performed and the biological behavior of the nanocomposite was evaluated in rats bearing fibrosarcoma tumor.

RESULTS

Liver, blood and tumor were the most accumulated sites at 1 h after the injection, and the radiolabeled nanocomposite as a PET/MRI imaging agent showed fast depletion from body and acceptable tumor uptake.

CONCLUSION

Magnetic (Fe3O4) and fluorescent components (CdTe QDs) along with a positron-emitting radionuclide will help to design a multimodal imaging system (PET/MRI/OI) which will offer the advantages of combined imaging techniques and further possible used in localized radionuclide therapy. Overall, [68Ga] Ga-GO@Fe3O4-cys-CdTe QDs nanocomposite shows great promise as a radiolabeled imaging agent owing to high accumulation in tumor region.

CdTe quantum dots on gold-198 nano particles: introducing a novel theranostic agent

The influence of coating a CdTe quantum dots (QDs) layer on the 198Au nanoparticles (NPs) in biodistribution of 198Au nanoparticles was investigated. The 198Au nanoparticles were prepared by irradiating the highly pure metallic gold in Tehran research nuclear reactor and subsequently 198Au-NPs were synthesized and subjected to surface modification with cysteamine and CdTe QDs to form an adduct. The prepared nanomaterials were characterized with X-ray diffraction, radio thin layer chromatography, transmission electron microscopy, and scanning electron microscopy. In-vivo biodistribution and tumor avidity studies were performed by intravenously injecting of cysteamine@198AuNPs: CdTe QDs nanocomposite into rats. The %ID/g (percent of the initial dose per gram tissue weight) in dissected organs and Fibrosarcoma tumor specimens was then measured. The hydrophilicity of the cysteamine@198AuNPs was increased by surface modification with CdTe QDs. Rapid excretion from body and high tumor uptake for cysteamine@198AuNPs: CdTe QDs revealed that this radiotracer could potentially be used in nuclear medicine as a theranostic agent.

68Ga CdTe/CdS fluorescent quantum dots for detection of tumors: investigation on the effect of nanoparticle size on stability and in vivo pharmacokinetics

Background

Quantum dots (QDs)-based theranostics offer exciting new approaches to diagnose and therapy of cancer. To take advantage of the unique properties of these fluorescent QDs for different biomedical applications, their structures, size and/or surface chemistry need to be optimized, allowing their stability and functionalities to be tailored for different biomedical applications.

Methodology

Cadmium telluride/Cadmium sulfide QDs (CdTe/CdS QDs) were synthesized and their structure, size, photostability and functionalities as a bioprobe for detection of Fibrosarcoma tumors were studied and compared with Cadmium telluride (CdTe) QDs. Hence, CdTe/CdS QDs were labeled with 68Ga radionuclide for fast in vivo biological nuclear imaging. Using gamma paper chromatography (γ-PC), the physicochemical properties of the prepared labeled QDs were assessed. In vivo biodistribution and positron emission tomography (PET) imaging of the 68Ga@ CdTe/CdS QDs nanocrystals were investigated in Sprague Dawley® rats bearing Fibrosarcoma tumor.

Results

CdS shell on the surface of CdTe core increases the size and photostability against high energy radiations; therefore, CdTe/CdS QDs show prolonged fluorescence as compared to CdTe QDs.

Conclusion

Excellent accumulation in tumor was observed for core/shell quantum dots, but this study showed that small changes in the size of the QDs (+1 nm), after adding the CdS shell around CdTe core, greatly change their biodistribution (especially the liver uptake).

An Investigation on the Pharmacological Profile of Titanium (IV) and Aluminum (III) 8-Hydroxyquinoline Derivatives Grafted on MCM-41 Mesoporous Silica

8-hydroxyquinoline and 5-chloro-8-hydroxyquinoline were treated with a titanium (IV) and Aluminum (III) alkoxide reagents to generate (Q)2(2-BuO) Al (Q = 8-hydroxyquinoline and 5-chloro-8-hydroxyquinoline) and (Q)2(O-iPr)2Ti (Q = 5-chloro-8-hydroxyquinoline) complexes. These active complexes underwent successive grafting on MCM-41 mesoporous silica in order to improve overall toxicity and stability of them. The prepared nanocomposites were characterized. Anti-bacterial activity of the compounds on Escherchia coli (ATCC 1330), Salmonella typhi (PTCC 1609) and Staphylococcus aureus subsp. Areas (PTCC 1113) were tested and the anti-fungal activity of them was determined using the agar well diffusion assay method on SCC (for yeasts) and Muller Hinton Agar medium (for filamentous fungi). The results showed that the anti-microbial (bacterium and fungi) effect of the Ti & Al complexes can be improved in the solid-state using appropriate chlorine substituent on the 8-hydroxyquinoline ligand and grafting to the mesoporous silica.

68Ga@pyridine-functionalized MCM-41 mesoporous silica: a novel radio labeled composite for diagnostic applications

Silica nanoparticles (SNPs) are known as intrinsic radiolabeling agents and offer a fast and reliable approach to deliver theranostic agents into targeted organs. Radiolabeled amorphous silica nanoparticles are of great interest to radiation oncology communities. In order to improve the performance of these nano materials in cancer diagnosis and treatment, their inherent properties, such as surface area and the ability to accumulate in cancer cells, should be enhanced. Pyridine functionalized mesoporous silica MCM-41 is known as a potential anticancer-drug delivery system with high suface area. In thiswork, in order to produce an image-guided drug delivery system for diagnostic applications, [68Ga] radionuclide was grafted on pyridine functionalized MCM-41. The nanoparticles were assessed with atomic force microscopy (AFM), paper chromatography, X-ray diffraction, FTIR spectroscopy, CHN and TGA/DTA analyses. The pharmacokinetic profile evaluation of the radiolabeled nano silica, [68Ga]-Py-Butyl@MCM-41, was done in Fibrosarcoma tumor-bearing mice. This labeled nanocomposite with appropriate blood circulation in body, high structural stability, high tumor/blood ID/g% ratio and fast excretion from the body can be proposed as an efficient nano engineered composite for upcoming tumor targeting/imaging nanotechnology-based applications.

Synthesis, characterization and biological evaluation of a well dispersed suspension of gallium-68-labeled magnetic nanosheets of graphene oxide for in vivo coincidence imaging

Graphene oxide (GO) nanosheets were hybridized with Fe3O4 nanoparticles (NPs) to form magnetic GO (MGO) and were further labeled by [68Ga]GaCl3 as a potential drug delivery system. Paper chromatography, Fourier transform infra red (FTIR) spectroscopy, low-angle X-ray diffraction (XRD), CHN and atomic force microscopy (AFM) were utilized to characterize the trinary composite ([68Ga]@MGO). Biological evaluations of the prepared nanocomposite were performed in normal Sprague Dawley rats and it was found to be a possible host for theranostic radiopharmaceuticals. The results showed that the grafting of Fe3O4 NPs on nanocomposite reduced the unwanted liver and spleen uptakes and increased the ratio of kidney/liver uptake from 0.037 to 1.07, leading to the fast removal of radioactive agent and less imposed radiation to patients. The high level of hydrogen bonding caused by the presence of functional groups is responsible for this effect. Considering the accumulation of the tracer in vital organs of rat (especially brain), efficient iron oxide grafting, fast wash-out, the short half-life gallium-68 and less imposed radiation doses to patients, this nanocomposite could be a suitable candidate for positron emission tomography (PET) studies and imaging applications.

Preclinical dosimetric estimation of [111In] 5, 10, 15, 20-tetra phenyl porphyrin complex as a possible imaging/PDT agent

Introduction: Recent studies show that porphyrin derivatives have interesting pharmacological and photodynamic properties and wide range of usage in photodynamic therapy treatment. This study describes the preparation, biodistribution and absorbed dose prediction of [111In] labeled 5, 10, 15, 20-tetra phenyl porphyrin (TPP) in human organs, based on rats' biodistribution data. Methods: Five rats were sacrificed at each exact time intervals (2, 4 and 24 h post injection) and the percentage of injected dose per gram of each organ was measured by direct counting from rats data from 12 harvested organs. The Medical Internal Radiation Dose (MIRD) formulation was applied to extrapolate from rats to human and to project the absorbed radiation dose for various organs in humans. Results: From rat data we estimated that injection of [111In] TPP into the humans would result in an estimated effective absorbed dose of 0.09 mSv/MBq in the whole body. While the highest effective absorbed dose for 111In-TPP was in the heart wall (0.22 mSv), the organs that received the next highest doses were the Kidneys (0.06 mSv), thymus (0.04 mSv) and lungs (0.03 mSv). Conclusions: The skin dose will four times higher compare to the other 111In compounds, which was due to magnificent skin uptakes. According to the fast wash-out, tumor avidity and the short half-life, [111In] can be a suitable candidate for labeling of photo dynamic therapy (PDT) agents as a tracer for accurate biological evaluation of other PDT agents such as Photofrin and its homologs.

Structural and spectroscopic characterizations of tetra-nuclear niobium(V) complexes of quinolinol derivatives

Reactions between niobium ethoxide and 8-hydroxy-2-methylquinoline or 5-chloro-8-hydroxyquinoline have been explored. Two new tetranuclear heteroleptic niobium complexes containing oxo, ethoxo, and quinolinate chelate rings have been synthesized and characterized by (1)H, (13)C and (93)Nb NMR, UV-Vis, and FT-IR spectroscopies, and single-crystal X-ray diffraction. The molecular structures of the niobium complexes, [Nb4(μ-O)4(μ-OEt)2(ONC10H8)2(OEt)8] (I) and [Nb4(μ-O)4(μ-OEt)2(ONC9H5Cl)2(OEt)8] (II), are composed of a pair of edge-sharing bioctahedral moieties in which connected via two almost linear oxo-bridges, with a large difference in the NbO distances. Single-crystal structures showed both complexes are centrosymmetric and contain two distinct Nb centers, and results confirmed by observation of two niobium signals in the (93)Nb NMR spectra of complexes.

Production, quality control, biodistribution assessment and preliminary dose evaluation of [177Lu]-tetra phenyl porphyrin complex as a possible therapeutic agent

<p>Due to interesting therapeutic properties of ¹⁷⁷Lu and tumor avidity of tetraphenyl porphyrins (TPPs), ¹⁷⁷Lu-tetraphenyl porphyrin was developed as a possible therapeutic compound. ¹⁷⁷Lu of 2.6-3 GBq/mg specific activity was obtained by irradiation of natural Lu₂O₃sample with thermal neutron flux of 4 × 10¹³ n.cm^-2.s^-1. Tetraphenyl porphyrin was synthetized and labeled with ¹⁷⁷Lu. Radiochemical purity of the complex was studied using Instant thin layer chromatography (ITLC) method. Stability of the complex was checked in final formulation and human serum for 48 h. The biodistribution of the labeled compound in vital organs of wild-type rats was studied up to 7 d. The absorbed dose of each human organ was calculated by medical internal radiation dose (MIRD) method. A detailed comparative pharmacokinetic study was performed for ¹⁷⁷Lu cation and [¹⁷⁷Lu]-TPP. The complex was prepared with a radiochemical purity: >97±1% and specific activity: 970-1000 MBq/mmol. Biodistribution data and dosimetric results showed that all tissues receive approximately an insignificant absorbed dose due to rapid excretion of the complex through the urinary tract. [¹⁷⁷Lu]-TPP can be an interesting tumor targeting agent due to low liver uptake and very low absorbed dose of approximately 0.036 to the total body of human.</p>

Preparation and preliminary biological evaluation of radiogallium-labeled DTPA-amlodipine complex for possible L-type calcium channel imaging

A DTPA-conjugated amlodipine analog (DTPA-AMLO) 3, was prepared for possible voltage gated calcium channel imaging after radiolabeling with Ga-67. [67Ga]-DTPA-AMLO complex was prepared starting [67Ga]gallium chloride and DTPA-AMLO in 60–90 min at 50–60 ℃ in phosphate buffer. The partition co-efficient and stability of the tracer was determined in final solution (25 ℃) and presence of human serum (37 ℃) up to 24 h. The biodistribution of the labeled compound in wild-type rats were determined up to 72 h using organ counting and SPECT. The radiolabled complex was prepard in high radiochemical purity (>96%, RTLC and >98% HPLC) and significant specific activity (7–10 GBq/mmol). The log P for the complex was calculated as − 0.594, consistent with a water soluble complex. The tracer is mostly washed out through kidneys which were in full compliance with the amlodipine metabolism and imaging studies demonstrated the same behavior. The tracer uptake in organs with smooth muscles was observed in stomach, colon as well as intestine.

Development of [62Zn/62Cu]-DOTA-rituximab as a possible novel in vivo PET generator for anti-CD20 antigen imaging

In this study, zinc-62 was prepared at radiopharmaceutical grade (for 62Zn/62Cu generator production) using natCu(p, xn) reaction with the production yield of 5.9 mCi/μAh at 30 MeV proton energy (radiochemical separation yield >95%, radionuclidic purity >99% and radiochemical purity >99%). In the next step, rituximab was successively labeled with [62Zn]-ZnCl2 after conjugation with p-SCN-Bz-DOTA followed by molecular filtration and determination of the average number of DOTA conjugated per mAb (6:1) by spectrophotometric method. Radiochemical purity (>97%, measured by ITLC and HPLC), integrity of protein after radiolabeling (gel electrophoresis) and stability of [62Zn]-DOTA-rituximab (in final formulation, and human serum) were determined 1–8 h as well as biodistribution studies in wild-type rats followed by coincidence imaging for 6 h. However, the accumulation of the radiolabeled antibody was not consistent with the former reported rituximab conjugates. [62Zn]-labeled monoclonal antibodies and fragments can be prepared as potential in vivo PET generators for molecular imaging however, the search for application of stable zinc complexes must be continued.

Development of a radiothallium (III) labeld porphyrin complex as a potential imaging agent

Since 201Tl is widely used in SPECT and porphyrins are important biological carriers, we tried to obtain a stable complex between thallium and porphyrins. The thallium porphyrin complex was synthesized by reaction of 201Tl(III) with porphyrin at 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (H2PFPP) for 60 min at 100°C. The complex was analysed via TLC and HPLC stability (in the final formulation and human serum) and the partition coefficient of the complex was determined. The biodistribution of the labeled compound in vital organs of wild-type rats was investigated. The complex was prepared with high radiochemical purity (> 99% ITLC, > 99% HPLC, specific activity: 13–14 GBq/mmol) (log P = 1.92). The stability of the Tl+3-complex seems to be low since the complex or free thallium is rapidly cleared through the kidneys and the liver.

Synthesis and Evaluation of [(67)Ga]-AMD3100: A Novel Imaging Agent for Targeting the Chemokine Receptor CXCR4

In order to develop a possible C-X-C chemokine receptor type 4 (CXCR4) imaging agent for oncological scintigraphy, [⁶⁷Ga]-labeled 1,1′-[1,4-Phenylene-bis(methylene)]bis(1,4,8,11-tetraazacyclotetradecane) ([⁶⁷Ga]-AMD3100) was prepared by using [⁶⁷Ga]GaCl₃ and AMD-3100 for 2 h at 50 °C (radiochemical purity: >95% ITLC, >99% HPLC, specific activity: 1800–2000 TBq/mmol) in acetate buffer. The stability of the complex was checked in the presence of human serum (37 °C) and in the final formulation for four days. The biodistribution of the labeled compound in the vital organs of wild type Sprague-Dawley rats was determined and compared with that of the free Ga³⁺ cation up to 48 h. Considering the spleen as the target organ, the best target:non target ratios were obtained 48 h post-injection (spleen:blood ratio; 14.5 and spleen:muscle ratio; 88.4). Initial SPECT images and biodistribution results in the wild type rats matched each other and demonstrated rapid washout of the tracer from the urinary tract. SPECT images in human breast carcinoma-bearing mice demonstrated a detectable tumor uptake in 48 h post-injection.

The synthesis, radiolabeling and first biological evaluation of a new 166Ho-complex for radiotherapy of bone metastases

In this study, the 166Ho-triethylene tetramine hexa (methylene phosphonic acid) (166Ho-TTHMP) complex was prepared as a bone palliation agent. The complex was successfully prepared using an in-house synthesized TTHMP ligand and [166Ho]HoCl3. Ho-166 chloride was obtained by thermal neutron irradiation (1×1013 n cm−2 s−1) of natural Ho(NO3)3 samples, followed by radiolabeling and stability studies. Biodistribution studies were also performed in wild type rats. The complex was prepared with the specific activity of 3–5 GBq/mg and a high radiochemical purity > 99%, (checked by ITLC). The 166Ho-TTHMP complex was stable in the final preparation and in the presence of human serum (> 90%) up to 72 h. The biodistribution of 166Ho-TTHMP in wild-type rats demonstrated significant bone uptake compared to 166HoCl3 up to 48 h. SPECT imaging of the radiolabeled compound was demonstrated to be in complete accordance with the biodistribution data. The major uptake was observed for long bones including thigh bones as well as skull and also knee and vertebrae. Primary properties of 166Ho-TTHMP demonstrate that this new therapeutic agent can be a good choice for metastatic bone pains.

Radiosynthesis and Quality Control of [(67)Ga]-3,4-dimethoxylated Porphyrin Complex as a Possible Imaging agent

Radiolabeled porphyrins are potential tumor avid radiopharmaceuticals because of their impersonation in the human body, ability to complex various radionuclides, water solubility, low toxicity etc. In this work a radiogallium porphyrin complex has been developed. [(67)Ga] labeled 5,10,15,20-tetrakis(3,4-dimethoxyphenyl) porphyrin ([(67)Ga]-TDMPP) was prepared using freshly prepared [(67)Ga]GaCl3 and 5,10,15,20-tetrakis(3,4-dimethoxyphenyl) porphyrin (H2TDMPP) for 60 min at 100°C. Stability of the complex was checked in final formulation and human serum for 24 h, followed by biodistribution and imaging studies in wild type rats up to 24 h. The radiocomplex was obtained with radiochemical purity >99% (ITLC) and >98% (HPLC), specific activity: 12-15 GBq/mmol. The partition coefficient was determined (log P=1.63). A detailed comparative pharmacokinetic study performed for (67)Ga cation and [(67)Ga]-TDMPP. The complex was mostly washed out from the circulation through kidneys. Myocardial uptake was significantly observed by SPECT and biodistribution studies. Knee and shoulder joints demonstrated significant activity uptake in 2h post injection. Higher water solubility of the complex due to ionic nature of the complex is an advantage for rapid wash-out of the complex from the system, the complex has significant joint uptake compared to other radiolabeled porphyrins which the mechanisms are explained.

Development of a (68)Ga-Fluorinated Porphyrin Complex as a Possible PET Imaging Agent

AIM

Due to the interesting pharmacologic properties of porphyrins, the idea of developing a possible tumor imaging agent using PET by incorporating (68)Ga into a suitable porphyrin ligand was investigated.

METHODS

(68)Ga-labeled 5,10,15,20-tetrakis(pentafluoro-13 phenyl) porphyrin ((68)Ga-TFPP) was prepared using freshly eluted [(68)Ga]GaCl3 obtained from a 68Ge/68Ga generator developed in-house and 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (H2TFPP) for 60 min at 100°C.

RESULTS

The complex was prepared with high radiochemical purity (>99% ITLC, >99% HPLC, specific activity: 13-14 GBq/mmol). Stability of the complex was checked in the final formulation and in human serum for 5 h. The partition coefficient was calculated for the compound (log P = 0.62). The biodistribution of the labeled compound in vital organs of Swiss mice bearing fibrosarcoma tumors was studied using scarification studies and SPECT imaging up to 1 h. The complex was mostly washed out from the circulation through kidneys and liver. The tumor-to-muscle ratio 1 h post injection was 5.13.

CONCLUSION

The radiolabeled porphyrin complex demonstrated potential for further imaging studies in other tumor models.

Development of ga-67 maltolate complex as an imaging agent

Due to the antitumor activity of Gallium MAL complex, as well as recent findings on new targeted biomolecules in malignant cells through this complex, the development of radiolabeled gallium complex for future imaging studies was targeted. Ga-67 labeled 3-hydroxy-2-methyl-4H-pyran-4-onate (Ga-67 MAL) was prepared using freshly prepared Ga-67 chloride and 3-hydroxy-2-methyl-4H-pyran-4-onate in a sodium salt form in 25 min at 40° C. The stability of the complex was checked in final formulation and human serum for 24 h followed by the administration in Swiss mice for biodistribution studies. The complex was prepared in high radiochemical purity (> 97% ITLC, > 98% HPLC) and specific activity of 13-14 GBq/mmol and was stable in the presence of serum for 48 h. The partition coefficient was calculated for the compound (log p = 0.40). A detailed comparative pharmacokinetic study was performed for Ga-67 cation and Ga-67-MAL. The complex is more rapidly washed out from the circulation through kidneys and liver compared to Ga-67 cation and can be an interesting tumor imaging agent due to the fact that the cold compound is undergoing clinical trials as a safe and potential therapeutic agent for cancer.

Grafting of a novel gold(III) complex on nanoporous MCM-41 and evaluation of its toxicity in Saccharomyces cerevisiae

The goal of this research was to investigate the potential of newly synthesized gold complex trichloro(2,4,6-trimethylpyridine)Au(III) as an anticancer agent. The gold(III) complex was synthesized and grafted on nanoporous silica, MCM-41, to produce AuCl(3)@PF-MCM- 41 (AuCl(3) grafted on pyridine-functionalized MCM-41). The toxicity of trichloro(2,4,6- trimethylpyridine)Au(III) and AuCl(3)@PF-MCM-41 in Saccharomyces cerevisiae (as a model system) was studied. The gold(III) complex showed a mid cytotoxic effect on yeast viability. Using the drug delivery system, nanoporous MCM-41, the gold(III) complex became a strong inhibitor for growth of yeast cells at a very low concentration. Furthermore, the animal tests revealed a high uptake of AuCl(3)@PF-MCM-41 in tumor cells. The stability of the compound was confirmed in human serum.

Pyridine-functionalized MCM-41 as an efficient and recoverable catalyst for the synthesis of pyran annulated heterocyclic systems

Pyridine-functionalized MCM-41 catalyzed reactions between tetracyanoethylene and various activated CH-acid compounds are described. These reactions afford the corresponding pyran annulated heterocyclic ring systems in high yields at room temperature within a few minutes. The work-up procedure is very simple and the products do not require further purification. The catalyst can be recycled and reused for several times without observable loss of performance.

Bis(tribenzyl-ammonium) tetra-chloridoaurate(III) chloride

In the title compound, (C(21)H(22)N)(2)[AuCl(4)]Cl, the Au(III) atom adopts a square-planar coordination geometry defined by four chloride ions. In the crystal structure, inter-molecular N-H⋯Cl hydrogen bonds link the organic cations and the uncoordinated chloride ion.

Bis(μ-2-methyl-8-oxidoquinolin-1-ium-κO:O)bis-[(acetato-κO,O')(2-methyl-8-oxidoquinolin-1-ium-κO)bis-(nitrato-κO,O')lanthanum(III)]

The N-heterocycles in the centrosymmetric title compound, [La(2)(C(10)H(9)NO)(4)(CH(3)COO)(2)(NO(3))(4)], exist in the zwitterionic form. One heterocycle binds to a metal center whereas the other bridges two metal centers. Each La atom is chelated by an acetate and two nitrate groups and is surrounded by nine O atoms in a distorted tricapped trigonal-prismatic coordination environment. The N-H groups form intra-molecular N-H⋯O hydrogen bonds. One of the nitrate ions is disordered over two positions in a 0.80 (3):0.20 (3) occupancy ratio.

1'-Methyl-2-oxo-5'-phenyl-spiro-[indoline-3,3'-pyrrolidine]-4',4'-dicarbo-nitrile

The title spiro-compound, C₂₀H₁₆N₄O, crystallizes with four independent mol­ecules in the asymmetric unit. In all of them, the oxindole unit is planar, the r.m.s. deviations ranging from 0.07 to 0.08 Å, while the pyrrolinyl ring adopts an envelope conformation (with the N atom representing the flap). In the crystal, adjacent mol­ecules are linked by N—H⋯N and N—H⋯O hydrogen bonds.

Bis(μ-2-methyl-quinolin-1-ium-8-olato-κO:O')bis-[(2-methyl-quinolin-1-ium-8-olato-κO)tris-(nitrato-κO,O')lanthanum(III)]

The two independent N-heterocycles in the centrosymmetric title compound, [La₂(C₁₀H₉NO)₄(NO₃)₆], exist in the zwitterionic form. One of these binds to one metal center, whereas the other bridges two metal centers. The La atom is chelated by three nitrate groups and is surrounded by nine O atoms in a coordination environment based on a distorted monocapped square-anti­prism. The dinuclear structure is further stabilized by intra­molecular N—H⋯O(nitrate) hydrogen bonds.

Bis(5-chloro-quinolin-8-olato-κN,O)bis-(propan-2-olato-κO)titanium(IV)

The Ti^IV atom in the title compound, [Ti(C₉H₅ClNO)₂(C₃H₇O)₂], is chelated by the substituted quinolin-8-olate anions in a distorted octa­hedral geometry. The N-donor atoms are in a cis alignment as are the O atoms of the propan-2-olate groups; the O atoms of the quinolin-8-olate groups are trans to each other. One C atom of one propan-2-olate group is disordered over two positions with occupancies of 0.733 (8):0.267 (8).

Dichloridobis(5,7-dichloro-quinolin-8-olato-κN,O)tin(IV)

The Sn^IV atom in the title compound, [Sn(C₉H₄Cl₂NO)₂Cl₂], is chelated by the substituted quinolin-8-olate anions in a distorted octa­hedral geometry. The N-donor atoms are in a cis alignment as are the Cl atoms; the O atoms are trans to each other.

Bis(isopropoxido-κO)bis-(2-methyl-quinolin-8-olato-κN,O)titanium(IV)

The two 2-methyl­quinolin-8-olate anions in the title complex, [Ti(C₁₀H₈NO)₂(C₃H₇O)₂], chelate the Ti^IV atom, which shows an all-cis distorted octa­hedral N₂O₄ coordination geometry.

8-Hydroxy-2-methylquinoline

The asymmetric unit of the title compound, C₁₀H₉NO, contains two independent mol­ecules which are linked by a pair of O—H⋯N hydrogen bonds into a hydrogen-bonded dimer.