Single Crystal X-ray Diffraction Determination Research Articles

Post-modified thiacalix[4]arene-based Ni16-NH2 cluster by ferrocene for synergistic photothermal conversion property

A high-nuclearity Ni16-NH2 cluster, namely {[Ni4(TC4A)Cl]4 (5-NH2-BDC)8}[(CH3)2NH2]4 (+solvents), has been solvothermal synthesized by the modular condense of four Ni4-TC4A (H4TC4A = p-tert-butylthiacalix[4]arene) polynuclear second-building units (PSBUs) and eight 5-NH2-BDC ligands (5-NH2-H2BDC = 5-amino-1,3-benzene dicarboxylic acid). The Ni16-NH2 is characterized by a quadrangular arrangement of Ni4-TC4A PSBUs and two pairs (each of four) exposed –NH2 groups on both sides of the cluster, which was structurally revealed by single crystal X-ray diffraction determination. A series of Ni16-Fc-x (x = [Fc-CHO]/ [Ni16-NH2], x = 1, 2, 4, 8) complexes were synthesized by post-modification of Ni16-NH2 with Fc-CHO via the Schiff Base Reaction and characterized by UV–Vis, FT-IR, and XPS measurements. The fabricated Ni16-Fc-4/8 exhibited synergistic photothermal conversion properties of the Ni16-NH2 cluster and Fc groups.

Polymorphs, Solvatomorphs, Hydrate, and Perhydrate of Dabrafenib

Crystal form screening of the anticancer drug dabrafenib (DBF) was performed using a wide range of nonpolar aprotic, polar aprotic, and polar protic solvents. Extensive crystallization in these solvent systems produced three crystal forms (I, II, and III) of the drug, a monohydrate, an isomorphous peroxo solvate, and eight different solvates with ethyl acetate, dichloromethane, chloroform, carbon tetrachloride, 1,1,2,2-tetrachloroethane, tetrachloroethylene, benzene, and anisole of DBF. Surprisingly no solvates were crystallized with the alcohol solvents attempted. The novel crystalline forms were characterized by single-crystal X-ray diffraction (SC-XRD) or structure determination from powder data (SDPD). The neutral drug derived from the mesylate salt of DBF by neutralization (form Ia) and the crystallized form I exhibited almost a similar powder XRD line pattern but their differential scanning calorimetry (DSC) thermograms comparison showed significant differences. Thus, the structure of microcrystalline powder form Ia was solved from SDPD reflections and showed the same molecular packing but different conformational strain compared to form I (structure by SC-XRD). The relative stability of the drug polymorphs was calculated using dispersion-corrected density functional theory with an intramolecular conformational energy correction. The calculations suggest that form II is the most stable polymorph and form III, form I, and form Ia are progressively less stable. Residual water content analysis of the isomorphous peroxosolvate showed that it is a mixed hydrate/peroxosolvate with ∼9.5% water occupancy quantified by 31P nuclear magnetic resonance analysis of the peroxosolvate content using triphenylphosphine oxide. The supramolecular analysis and molecular packing of DBF crystal forms suggest that the molecule has a propensity to form solvates with aprotic solvents and more specifically with chlorohydrocarbons. With its high molecular flexibility, prolific solvate potential, and drug polymorphism, the present work opens the opportunity for further solid-form landscape study of the popular anticancer drug DBF.

Binuclear silver(I) complexes with the non-steroidal anti-inflammatory drug tolfenamic acid: Synthesis, characterization, cytotoxic activity and evaluation of cellular mechanism of action

In this study, two new binuclear silver(I)-tolfenamic acid complexes including picoline derivative ligands, [Ag2(μ-tolf)2(2-pic)2] 1and [Ag2(μ-tolf)2(4-pic)2] 2, were synthesized and identified by elemental analysis, FT-IR, 1H NMR and thermal analysis techniques. The in vitro cytotoxicity of the complexes was investigated against human breast cancer cell lines by XTT, flow cytometry, enzyme activity and western blot studies. The structures of 1 and 2 were clarified by single-crystal X-ray diffraction determination. The data clearly indicated that the Ag(I) ion is coordinated to one auxiliary ligand (2-pic or 4-pic), two tolfenamato ligands and another Ag(I) ion, demonstrating a distorted tetrahedral geometry. The tolfenamato ligands act as a bridging bidentate ligands. The chains are stabilized by intramolecular Ag(I)⋯π and π···π interactions. The 1H NMR and thermal analyses displayed the presence of picoline and tolfenamato ligands in the coordination sphere and the purity of the complexes. Both complexes exhibited potent cytotoxicity against cancer cell lines with higher selectivity than carboplatin. Flow cytometry and enzyme activity studies indicated that both complexes caused an increase in apoptosis, ROS and NO levels, cell cycle arrest, mitochondrial membrane damage and caspase activity, as well as inhibiting PI3K/Akt phosphorylation and modulating the oxidant/antioxidant balance system. Western blot analyses revealed the up-regulation of bax, caspase-3, caspase-9 and p53 proteins, but the down-regulation of bcl-2. These results demonstrate the vigorous apoptotic potential of the novel Ag(I) complexes in human breast cancer MDA-MB-453 cells.

A combined model of electron density and lattice dynamics refined against elastic diffraction data. Thermodynamic properties of crystalline L-alanine.

Thermodynamic stability is an essential property of crystalline materials, and its accurate calculation requires a reliable description of the thermal motion - phonons - in the crystal. Such information can be obtained from periodic density functional theory (DFT) calculations, but these are costly and in some cases insufficiently accurate for molecular crystals. This deficiency is addressed here by refining a lattice-dynamics model, derived from DFT calculations, against accurate high-resolution X-ray diffraction data. For the first time, a normal-mode refinement is combined with the refinement of aspherical atomic form factors, allowing a comprehensive description and physically meaningful deconvolution of thermal motion and static charge density in the crystal. The small and well diffracting L-alanine system was used. Different lattice-dynamics models, with or without phonon dispersion, and derived from different levels of theory, were tested, and models using spherical and aspherical form factors were compared. The refinements indicate that the vibrational information content in the 23 K data is too small to study lattice dynamics, whereas the 123 K data appear to hold information on the acoustic and lowest-frequency optical phonons. These normal-mode models show slightly larger refinement residuals than their counterparts using atomic displacement parameters, and these features are not removed by considering phonon dispersion in the model. The models refined against the 123 K data, regardless of their sophistication, give calculated heat capacities for L-alanine within less than 1 cal mol-1 K-1 of the calorimetric measurements, in the temperature range 10-300 K. The findings show that the normal-mode refinement method can be combined with an elaborate description of the electron density. It appears to be a promising technique for free-energy determination for crystalline materials at the expense of performing a single-crystal elastic X-ray diffraction determination combined with periodic DFT calculations.

Synthesis, structure, antidiabetic and antioxidant properties of a new Co(II) complex with a flexible tripodal ligand

A novel 3D Co(II) complex {[Co3(TTTMB)4(SCN)6]·3.5H2O}n (1) has been synthesized through the reaction of a flexible tripodal ligand 1,3,5-tris(triazol-1-ylmethyl)- 2,4,6-trimethylbenzene (TTTMB) with Co(NO3)2 and KSCN. Single crystal X-ray diffraction determination shows that complex 1 crystallizes in the monoclinic space group C2/c and exhibits three crystallographically independent Co(II) ions with the similar coordination environment but different bond lengths and angles. The overall structure of complex 1 can be described as a (3,4)-connected network with the topological notation of (4·82)2(84·122)(42·84)2. The antidiabetic activity against α-amylase and antioxidant activity against 1,1-diphenyl-2-picrylhydrazil (DPPH) of complex 1 are evaluated in vitro. The IC50 values of the complex 1 on α-amylase and DPPH are 1.27 mg/mL and 1.53 mg/mL, respectively, which are lower than those of corresponding standard acarbose (2.89 mg/mL) and vitamin E (2.39 mg/mL), indicating that the complex 1 is a new potential antidiabetic and antioxidant drug. Additionally, the solid-state fluorescent properties and thermal stability of the complex are investigated at room temperature.

A Flexible Microporous Hydrogen-Bonded Organic Framework

A dynamic hydrogen-bonded organic framework, HOF-12, has been synthesized from 1,3,5-tris(4-carboxyphenyl)-2,4,6-trismethylbenzene and crystallographically characterized. Through single-crystal X-ray diffraction determination, the hydrogen-bonded supramolecular architecture with a pore size of 8.6 × 10.8 A2 has been identified, which consists of six interpenetrated carboxyl-linked 6,3-topological networks. The powder X-ray diffraction analysis and the giant hysteresis sorption of carbon dioxide at 196 K demonstrate the obvious contraction of the degassed hydrogen-bonded framework, exhibiting a high CO2 uptake of 328 cm g–1 at 1.0 atm.

Syntheses, structures, and luminescence of a series of novel trimetallic coordination polymers constructed by Cu-I clusters and alkaline-carboxyl- alkaline-earth building units

Seven novel trimetallic coordination polymers, namely, [Li2SrCu2I2(IN)4(DMF)3]n·nDMF (1), [LiSr2Cu2I2(IN)5(DMF)2]n (2), [NaSr2Cu2I2(IN)4(NO3)(DMF)4]n·nDMF·0.5nH2O (3), [NaSr2Cu2I2(IN)5(DMF)4]n·3nDMF·3nH2O (4), [Li2BaCu2I2(IN)4(DMF)3]n·nDMF (5), [Li2Ba2Cu2I2(IN)4(OAc)2(DMF)3]n·nDMF·0.5nH2O (6), [Li2Ba2Cu2I(IN)7(H2O)1.5]n·0.5nH2O (7) (IN = isonicotinic anion, DMF = N, N-dimethylformamide) have been synthesized via solvothermal method. All of the coordination polymers were characterized by single-crystal X-ray diffraction, FT-IR spectroscopy, elemental analysis and thermogravimetric analysis. Single-crystal X-ray diffraction determinations revealed that compounds 1–7 were three dimensional frameworks. Compounds 1–6 were assembled by Cu2I2 units and different alkaline-carboxyl- alkaline-earth rod building units with different topologies; while, compound 7 was constructed by Cu2I units and alkaline-carboxyl- alkaline-earth honeycomb layers. The photoluminscent investigations revealed that the compounds 1, 3, 5 and 6 emitted strong yellow, while compounds 2, 4 and 7 emitted strong orange light.

Photophysical investigaions and the bioimaings of α-, β-, γ-pyridine-based terpyridine derivatives

Three unprecedented triphenylamine-based D-A type terpyridine derivatives (TriphenL1-TriphenL3) with different positions of nitrogen atom in the terpyridine moiety were carefully designed and fully characterized, which was further confirmed via single-crystal X-ray diffraction determination. The photophysical properties of all the three compounds were comprehensively studied by both theoretical calculations and experimental techniques, which revealed that TriphenL3 with γ-pyridine in the NIR region possessed large two-photon absorption cross-section. Experiments including photophysical tests and cytotoxicity demonstrated these dyes were characterized with larger Stokes shifts, longer fluorescence lifetime, low toxicity and good cell penetrability, thus TriphenL1-TriphenL3 were succeed to be devoted as cell stains, suggesting a prospect for applications of in vitro and vivo cellular imaging.

Novel D-π-A-π-D structural 2, 2′-bipyridine derivatives with different electron donors: Structure, one- and two-photon excited fluorescence and bioimaging

Two novel D-π-A-π-D structural 2,2′-bipyridine derivatives based on different electron donors, namely aza-crown ether and triphenylamine groups were synthesized and characterized. One of which was characterized by single crystal X-ray diffraction determination. Their linear photophysical properties were systematically investigated in various solvents. The two-photon excited fluorescence were investigated. The two dyes both exhibited excellent one- and two-photon excited fluorescence as well as high quantum yield and large two-photon absorption cross-section (δ). Fluorescence microscopy imaging of them in NIH/3T3 cell line was studied. The result indicated that both of them exhibit excellent biological compatibility.

Synthesis, characterization and antitumor activity of palladium(II) complexes of imidazolidine-2-thione

Complexes of the type cis-[PdX2(imzt)(PPh3)] {imzt = imidazolidine-2-thione; PPh3 = triphenylphosphine; X = Cl (1), Br (2), I (3), SCN (4)} have been synthesized and characterized by elemental analyses, molar conductance, IR and 1H NMR spectroscopies. The complex 1·MeOH was obtained from the reaction of [PdCl2(CH3CN)2], imidazolidine-2-thione and triphenylphosphine in CHCl3/CH3OH. Complexes 2·MeOH, 3 and 4 were prepared by metathesis of the chlorido ligands in 1 with bromide, iodide and thiocyanate, respectively. Elemental analyses showed good agreement with the expected mononuclear compositions, while the molar conductivities of the complexes in DMF were consistent with their nonelectrolytic nature. NMR spectra confirmed coordination of the imidazolidine-2-thione and triphenylphosphine ligands. Single-crystal X-ray diffraction determination of 1·CH3OH showed that the coordination geometry around PdII is nearly square planar, with the chlorido ligands in a cis configuration. All four complexes have been tested in vitro by XTT assay for their cytotoxicity against human glioblastoma cell line (U87MG). The binding of 1 with guanosine was studied by 1H NMR spectroscopy, revealing that the coordination takes place via N7.

Dinuclear Zinc(II) Macrocyclic Complex as Receptor for Selective Fluorescence Sensing of Pyrophosphate.

A new diethylenetriamine-derived macrocycle known as L, bearing 2-methylquinoline arms and containing m-xylyl spacers, was prepared in good yield by a one-pot [2 + 2] Schiff base condensation procedure, followed by reduction with sodium borohydride. Up to now this is the first hexaazamacrocycle with appended fluorophore units. Single-crystal X-ray diffraction determination of the dinuclear zinc(II) complex of L showed that metal centers are located at about 7.20(2) Å from one another. This complex exhibits only weak fluorescence in aqueous solution, but the addition of 1 equiv of pyrophosphate (PPi) caused a 21-fold enhancement of the fluorescence intensity. The sensor response is linear up to a value of 10 μM HPPi(3-) and has a detection limit of 300 nM. The receptor behaves as a highly selective sensor for pyrophosphate as other anions, including phosphate, phenylphosphate (PhP), adenosine monophosphate (AMP), adenosine diphosphate (ADP), and adenosine triphosphate (ATP), failed to induce any fluorescence change and practically do not affect the fluorescence intensity of the sensor in the presence of HPPi(3-). Competition titrations carried out in aqueous solution at pH 7.4 [in 20 mM 3-(N-morpholino)propanesulfonic acid (MOPS) buffer] by spectrofluorometry revealed a high association constant value of 6.22 log units for binding of PPi by the dinuclear zinc(II) receptor, one of the highest reported values for colorimetric/fluorometric sensors able to work under real aqueous physiological conditions, while association constant values for binding of the other phosphorylated substrates are in the 5.51-4.03 log unit range.

Structural and energetic characterization of anhydrous and hemihydrated 2-mercaptoimidazole: Calorimetric, X-ray diffraction, and computational studies

This paper reports an experimental and theoretical study on the structural and energetic characterization of the 2-mercaptoimidazole (2-MI) in the solid and in the gaseous phases. The single crystal X-ray diffraction determinations on the anhydrous and hemihydrate 2-MI forms were carried out at T=(296±2)K and T=(150±2)K, respectively, and suggest that in both forms the 2-MI molecule is closer to the thione conformation, albeit some single bond character is possible.The energy of combustion of the title compound was measured by rotating-bomb combustion calorimetry, being used to derive the corresponding enthalpy of formation in the crystalline-phase. The enthalpy of sublimation of 2-MI, at T=298.15K, was obtained from high temperature Calvet microcalorimetry measurements. These two parameters yielded the gas-phase enthalpy of formation, allowing the inherent energetic analysis of the molecule. This result was discussed together with the corresponding predictions for 2-MI and its tautomer, 1,3-dihydro-2H-imidazole-2-thione, by the G3 method.The dehydration reaction of 2-MI·0.5H2O(cr) was also investigated and the corresponding enthalpy of dehydration was determined by Calvet microcalorimetry.

Tetramic Acids and Pyridone Alkaloids from the Endolichenic Fungus Tolypocladium cylindrosporum

Three new tetramic acid derivatives, tolypocladenols A1, A2, and B (1-3), a new pyridone alkaloid, tolypyridone A (4), and a new coumarin derivative, 3,8-dihydroxy-4-(4-hydroxyphenyl)-6-methylcoumarin (5), together with four known compounds (6-9) were isolated from the endolichenic fungus Tolypocladium cylindrosporum, which inhabits the lichen Lethariella zahlbruckneri. Structures of these compounds were determined by comprehensive analysis of spectroscopic data and single-crystal X-ray diffraction determination. Bioassay of the isolated compounds found that pyridoxatin (7) was cytotoxic to human cancer cells by induction of G0/G1 cell cycle arrest and apoptosis.

The first 3D Zn(II) complex involving chiral chains constructed by achiral ligand 2-(hydroxymethyl)-1H-imidazole-4,5-dicarboxylate

A novel 3D Zn(II) complex [Zn(H2hmIDC)]n (1) has been synthesized through the reaction of an achiral ligand 2-(hydroxymethyl)-1H-imidazole-4,5-dicarboxylic acid (H4hmIDC) with Zn(NO3)2. Single crystal X-ray diffraction determination shows that complex 1 is the first 3D framework based on left and right-handed helical chains, in which all of the H2hmIDC2− ligands coordinate to Zn(II) ions with μ3-bridging mode. The overall structure of complex 1 can be described as a (3,3)-connected topology with the topological notation of {82·10}2. The TG analysis shows that it possesses great thermal stability. In addition, its IR spectra, PXRD pattern and fluorescence property have been investigated.

Pyrazolyl Pd(II) complexes containing triphenylphosphine: Synthesis and antimycobacterial activity

Complexes of the type trans-[PdCl2(HL)(PPh3)], where HL=pyrazole (1); 3,5-dimethylpyrazole (2); 4-nitropyrazole (3); 4-iodopyrazole (4) and PPh3=triphenylphosphine, were synthesized and characterized by elemental analyses, infrared and 1H NMR spectroscopies. Single-crystal X-ray diffraction determination on 3·0.9 CHCl3 and 4 showed that the coordination geometry around Pd(II) is nearly square-planar, with the chloro ligands in a trans configuration. In vitro antimycobacterial evaluation demonstrated that compound 4 displayed a minimum inhibitory concentration (MIC) of 7.61±2.18μM, being superior to the values observed for some commonly used antituberculosis drugs and other metal-based complexes.

Syntheses, Structures, and Properties of Two New Isostructural Complexes Based on 1-((Benzotriazol-1-yl)methyl)-1H-1,3-Imidazole and 1,4-Benzenedicarboxylate

Self-assemblies of Co(II) or Zn(II) salts with 1-((benzotriazol-1-yl)methyl)-1H-1,3-imidazole (bmi) and 1,4-benzenedicarboxylic acid (1,4-H2bdc) gave rise to two new isostructural complexes, [Co(bmi)2(bdc)]n (1) and [Zn(bmi)2(bdc)]n (2). Single-crystal X-ray diffraction determination shows that both complexes possess similar chain structure, in which two carboxylate groups of each bdc2– anion coordinate to metal ions with chelating mode and the bmi groups hang at both sides of the chains with monodentate mode. Complexes 1 and 2 are further extended to 3-D supramolecular structures by π–π interaction and intermolecular force. IR spectra, PXRD patterns, fluorescent properties and thermostability of both complexes have been investigated.

Dicarboxylate recognition properties of a dinuclear copper(II) cryptate.

A ditopic polyamine macrobicyclic compound with biphenylmethane spacers was prepared, and its dinuclear copper(II) complex was studied as a receptor for the recognition of dicarboxylate anions of varying chain length in H2O/MeOH (50:50 (v/v)) solution. The acid-base behavior of the compound, the stability constants of its complexes with Cu(2+) ion, and the association constants of the copper(II) cryptate with succinate (suc(2-)), glutarate (glu(2-)), adipate (adi(2-)), and pimelate (pim(2-)) were determined by potentiometry at 298.2 ± 0.1 K in H2O/MeOH (50:50 (v/v)) and at ionic strength 0.10 ± 0.01 M in KNO3. The association constants of the same cryptate as receptor for aromatic dicarboxylate substrates, such as phthalate (ph(2-)), isophthalate (iph(2-)), and terephthalate (tph(2-)), were determined through competition experiments by spectrophotometry in the UV region. Remarkably high values of association constants in the range of 7.34-10.01 log units were found that are, to the best of our knowledge, the highest values of association constants reported for the binding of dicarboxylate anions in aqueous solution. A very well defined peak of selectivity was observed with the binding constant values increasing with the chain length and reaching the maximum for substrates with four carbon atoms between the carboxylate groups. Single-crystal X-ray diffraction determinations of the cascade complexes with adi(2-) and tph(2-) assisted in the understanding of the selectivity of the cryptate toward these substrates. The Hirshfeld surface analyses of both cascade complexes suggest that the establishment of several van der Waals interactions between the substrates and the walls of the receptor also contributes to the stability of the associations.

Metal Coordination Polymers of 2,3‐Bisimidazol‐1‐ylquin­oxaline: Syntheses, Crystal Structures, and Luminescent Properties

AbstractThree new metal‐organic coordination polymers, namely, [Zn(μ2‐BiImQuin)(OAc)2]·H2O (1), [Zn(μ2‐BiImQuin)2(H2O)2]2·4Cl·H2O (2), and [Mn(μ2‐BiImQuin)2(N3)2]·4H2O (3) were prepared by reaction of the corresponding transition metal salt with new rigid ligand 2,3‐bisimidazol‐1‐ylquinoxaline (L) with diffusion or solution methods (BiImQuin = 2,3‐bisimidazol‐1‐ylquinoxaline). All the complexes were characterized by elemental analysis, IR, TGA, PXRD, and single crystal X‐ray diffraction determination. A one‐dimensional single chain was observed in complex 1, however one‐dimensional bead‐like double chains were observed in complexes 2 and 3. In the three complexes, the rigid didentate ligands bridged the metal ions into similar “zigzag” chain, and two “zigzag” chains are arranged into bead‐like double chain in complexes 2 and 3, where each metal ion is coordinated with four different didentate BiImQuin rather than two. On the other hand, the anions do great influence on the final supramolecular structure through coordination behavior and hydrogen‐bonding interactions. The complexes 1 and 2 display strong room temperature photoluminescence in visible region, which may be assigned to ligand‐to‐metal charge‐transfer.

Synthesis, Crystal Structure, and Property of a Ce(IV) Complex Based on 2,2′-(ethane-1,2-diyl)bis (1H-imidazole-4,5-dicarboxylic acid)

A new complex with the formula [Ce(SO4)(H2ebidc)1/2(H2O)5]n (1) has been synthesized through the self-assembly of Ce(SO4)2 with N-Heterocyclic carboxylic acid 2,2′-(ethane-1,2-diyl)bis(1H-imidazole-4,5-dicarboxylic acid) (H6ebidc). Single-crystal X-ray diffraction determination shows that complex 1 possesses an infinite 2-D grid network structure in which both the tetradentate H2ebidc4– group and SO2– 4 anion coordinate to Ce(IV) ions in bridging mode. The adjacent layers are connected through the hydrogen bonds resulting in a three-dimensional packing structure in the solid state. In addition, the luminescent property has been investigated.

Synthesis, characterization and pre-clinical evaluation of99mTc-tricarbonyl complexes as potential myocardial perfusion imaging agents

Myocardial perfusion imaging is an established Nuclear Medicine investigation. Current myocardial perfusion imaging agents sestamibi and tetrofosmin have number of drawbacks; low heart uptake coupled with uptake into the surrounding tissues leads to a poorer image quality. There is a need for continued research into designing and evaluating potentially superior myocardial imaging agents. Tri-carbonyl-technetium and rhenium complexes were prepared by combination with mono-dentate and bi-dentate ligands. Complexes were characterized by HPLC, MAS, nuclear magnetic resonance, infrared, single-crystal X-ray diffraction and partition coefficient determinations. (99m) Tc(CO)3 complexes were administered intravenously to Sprague Dawley rats, and tissue distribution studies were carried out at 15 min and 1 h p.i. Radiochemical purity was assessed as >90%. 1-10-phenanthroline, 2,2'-bipyridine and imidazole complexes gave the highest heart uptake. The percentage injected dose per gram (n = 3) at 1 h for 1-10-phenanthroline/imidazole was blood 0.21 ± 0.01, heart 1.12 ± 0.11, kidney 3.61 ± 1.13, liver 0.62 ± 0.06, lung 0.28 ± 0.12, spleen 0.24 ± 0.05, small intestine contents 1.87 ± 0.92; and for 2,2'-bipyridine /imidazole was blood 0.23 ± 0.02, heart 1.07 ± 0.18, kidney 3.31 ± 1.28, liver 0.56 ± 0.09, lung 0.14 ± 0.02, spleen 0.2 ± 0.1, small intestine content 1.05 ± 0.48. Further investigation to evaluate more complexes based on 1,10-phenanthroline, 2,2'-bipyridine and imidazole derivatives could potentially lead to agents with an increased heart uptake and faster clearance from the liver and gastrointestinal tract.