Nanoparticles: Taking a Unique Position in Medicine

The human nature of curiosity, wonder, and ingenuity date back to the age of humankind. In parallel with our history of civilization, interest in scientific approaches to unravel mechanisms underlying natural phenomena has been developing. Recent years have witnessed unprecedented growth in research in the area of pharmaceuticals and medicine. The optimism that nanotechnology (NT) applied to medicine and drugs is taking serious steps to bring about significant advances in diagnosing, treating, and preventing disease-a shift from fantasy to reality. The growing interest in the future medical applications of NT leads to the emergence of a new field for nanomaterials (NMs) and biomedicine. In recent years, NMs have emerged as essential game players in modern medicine, with clinical applications ranging from contrast agents in imaging to carriers for drug and gene delivery into tumors. Indeed, there are instances where nanoparticles (NPs) enable analyses and therapies that cannot be performed otherwise. However, NPs also bring unique environmental and societal challenges, particularly concerning toxicity. Thus, clinical applications of NPs should be revisited, and a deep understanding of the effects of NPs from the pathophysiologic basis of a disease may bring more sophisticated diagnostic opportunities and yield more effective therapies and preventive features. Correspondingly, this review highlights the significant contributions of NPs to modern medicine and drug delivery systems. This study also attempted to glimpse the future impact of NT in medicine and pharmaceuticals.

Crystal and molecular structure of [Ni{2-H2NC(=O)C5H4N}2(H2O)2][Ni{2,6-(O2C)2C5H3N}2]·4.67H2O; DFT studies on hydrogen bonding energies in the crystal

[Ni{2-H₂NC(=O)C₅H₄N}₂(H₂O)₂][Ni{2,6-(O₂C)₂C₅H₃N}₂]·4.67H₂O, a new complex salt containing a bis(2,6-dicarboxypyridine)nickel(II) anion and a bis(2-amidopyridine)diaquanickel(II) cation, was synthesized and characterized. The crystal is stabilized by an extensive network of hydrogen bonds. Alternate layers of anions and cations/water molecules parallel to (010) can be distinguished. Computational studies of the network packing of the title compound by high-level DFT-D/B3LYP calculations indicate stabilization of the networks with conventional and non-conventional intermolecular O-H...O, N-H...O and C-H...O hydrogen bonds along with π-stacking contacts. Due to the presence of water molecules and the importance of forming hydrogen bonds with the involvement of water clusters to the stability of the crystal packing, the importance and role of these water clusters, and the quantitative stability resulting from the formation of hydrogen bonds and possibly other noncovalent bonds such as π-stacking are examined. The binding energies obtained by DFT-D calculations for these contacts indicate that hydrogen bonds, especially O-H...O and N-H...O, control the construction of the crystalline packing. Additionally, the results of Bader's theory of AIM for these interactions agree reasonably well with the calculated energies.

Influence of 2-Amino-4-methylpyridine and 2-Aminopyrimidine Ligands on the Malonic Acid-Cu(II) System: Insights through Supramolecular Interactions and Photoresponse Properties

Two Cu(II)-malonate complexes with 2-amino-4-methylpyridine (complex 1) and 2-aminopyrimidine (complex 2) auxiliary ligands were synthesized, and their single-crystal X-ray diffraction structures were established. Change in the auxiliary ligand exhibits substantial structural variation in the present complexes. Complex 1 shows a one-dimensional anionic copper-malonate moiety connected by the malonate bridge, whereas complex 2 is a mononuclear one. For both the complexes, auxiliary ligands are attached with the Cu-malonate moiety through various noncovalent interactions. Optical band gap, electrical conductivity, and photosensitivity of complexes 1 and 2 were measured, but the values of electrical parameters of the complexes significantly differ from each other. However, the magnitudes of electrical parameters increase several times for both the complexes when they are exposed under visible light, though the values of light sensing parameters of complex 1 were found to be higher than those of complex 2. Density functional theory calculations for complex 1 were carried out to support the experimental result.

Effects of N-oxidation on the molecular and crystal structures and properties of isocinchomeronic acid, its metal complexes and their supramolecular architectures: experimental, CSD survey, solution and theoretical approaches

Nine coordination complexes and polymer (M/L/X) based on Co, Ni, Zn, Cu (M), pyridine-N-oxide-2,5-dicarboxylic acid (H2pydco) (L) and either isonicotinamide (Ina), piperazine (pipz), 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen) (X) were synthesized and characterized by elemental analyses, infrared spectroscopy and single crystal X-ray diffraction. The resulting empirical formulae of the prepared complexes are [Co(H2O)6][Co(pydco)2(H2O)2]·2H2O (1), [M(pydco)(H2O)4]2 [M = Co (2), Ni (3), Zn (4)], [Co(pydco)(bipy)(H2O)2]·4H2O (5), [Co(pydco)(phen)(H2O)2]·5.135(H2O)·0.18(EtOH) (6), [Cu(Hpydco)(bipy)Cl]·2H2O (7), [Cu(Hpydco)(bipy)Cl]2·2H2O (8), and {[AgCu(H2O)2(phen)(pydco)]NO3} n (9). With the exception of 9, which forms an extended structure via multiple coordination modes, all the complexes contain (H)pydco as a bidentate ligand coordinated to the metal ion via the N-oxide and the adjacent carboxylate group oxygen atom, creating a chelate ring. The metal centers exhibit either distorted octahedral (1-6) or square pyramidal (7-9) geometry. Our results demonstrate that, when acting cooperatively, non-covalent interactions such as X-H⋯O hydrogen bonds (X = O, N, C), C-O⋯π and π⋯π stacking represent driving forces for the selection of different three-dimensional structures. Moreover, in compounds 2-4, 1D supramolecular chains are formed where O⋯π-hole interactions are established, which unexpectedly involve the non-coordinated carboxylate group. The non-covalent interaction (NCI) plot index analysis reveals the existence of the O⋯π-hole interactions that have been evaluated using DFT calculations. The Cremer and Pople ring puckering parameters are also investigated. The complexation reactions of these molecules with M were investigated by solution studies. The stoichiometry of the most abundant species in the solution was very close to the corresponding crystals. Finally, the effect of N-oxidation on the geometry of complexes has been also studied using the Cambridge Structural Database. It shows that complexes containing N-oxidized H2pydc are very rare.

Nitrosalicylatocopper(II) complexes with chelating pyridine derivatives

Three new nitrosalicylatocopper(II) complexes have been prepared and characterized. Compounds of the composition Cu(5-NSal)2(2-ampy)2 (1), Cu(5-NSal)2(2-hmpy)2 (2) and Cu(3,5-DNSal)2(2-hmpy)2 (3), where 2-ampy = (2-aminomethyl)pyridine, 2-hmpy = (2-hydroxymethyl)pyridine, 5-NSal = 5-nitrosalicylate anion and 3,5-DNSal = 3,5-dinitrosalicylate anion, were characterized by elemental analyses, EPR and IR spectroscopy. EPR spectra are consistent with the dx2-y2ground electronic state. Spectral properties have shown “classic” monodentate coordination of 5-nitrosalicylate anion. Similarly, bonding mode of the 3,5‑dinitrosalicylate anion in (3) is assumed to be unidentate via the carboxyl group, which is surprising compared with the previously studied complex, where the preferred coordination via the phenolate group anion was observed.

CuII and ZnII β-diketonate coordination polymers based on pyrimidin-2-amine, pyrazine and 1,2-bis(4-pyridyl)ethane

Copper(II) and zinc(II) bis(4,4,4-trifluoro-1-phenylbutane-1,3-dionato) compounds with pyrimidin-2-amine (pyr2a), pyrazine (pyz) and 1,2-bis(4-pyridyl)ethane (dpet) were prepared and solid-state structures of coordination polymers [M(tfpb)₂(pyr2a)]_∞ [M = Cu (1), Zn (2); tfpb = 4,4,4-trifluoro-1-phenylbutane-1,3-dionate], [M(tfpb)₂(pyz)]_∞ [M = Cu (3), Zn (4a, 4b)] and [Cu(tfpb)₂(dpet)]_∞ (5), respectively, were determined by single-crystal X-ray analysis. The coordination of metal centers in all compounds is octahedral with nitrogen ligands occupying the axial positions. Compound (1) crystallizes in the triclinic space group P\bar 1, whereas (2) crystallizes in the monoclinic space group P2/n. Differences are due to the different orientation of adjacent M(tfpb)₂ units, whereas the orientation of pyrimidin-2-amine is the same in both compounds. Polymeric chains in (1) and (2) contain intramolecular N-H...O hydrogen bonding between amino and carbonyl groups. Room-temperature structures (3) and (4a) are isomorphous adopting the monoclinic space group C2/m; however, on cooling crystals (4a) to 150 K a single-crystal-to-single-crystal transformation to (4b) possessing the triclinic space group P\bar 1 was observed. Compound (5) crystallizes in the triclinic space group P\bar 1 and contains a parallel aggregation of chains in contrast to the known structure of the non-fluorinated benzoylacetonato ligand, where chains aggregate in a perpendicular fashion. In the compounds studied intramolecular C-H...O and/or C-H...F interactions are present. The neighboring chains are linked by π...π interactions and in some compounds also by C-H...π interactions [(1), (4b), (5)].

Importance of polarization assisted/resonance assisted hydrogen bonding interactions and unconventional interactions in crystal formations of five new complexes bearing chelidamic acid through a proton transfer mechanism

Five new coordination compounds derived from chelidamic acid and amines have been synthesized and X-ray characterized. The noncovalent interactions that govern the crystal packing have been rationalized by means of DFT calculations.

Synthesis, X-ray characterization and DFT studies of bis-N-imidazolylpyrimidine salts: the prominent role of hydrogen bonding and anion–π interactions

Five new compounds have been synthesized and characterized by elemental analysis, IR, NMR and single-crystal X-ray diffraction. They present interesting assemblies in the solid state dominated by H-bonding and anion–π interactions.

On the importance of non covalent interactions in the structure of coordination Cu(ii) and Co(ii) complexes of pyrazine- and pyridine-dicarboxylic acid derivatives: experimental and theoretical views

We synthesized and X-ray characterized four complexes based on pyrazine- and pyridine-dicarboxylic acid ligands. One of them exhibited a relevant lp–π-hole interaction.