In the current study, we evaluated the solubility of a number of organometallic species and showed that it is noticeably improved in diiodomethane when compared to other haloalkane solvents. The better solvation properties of CH I were associated with the substantially better σ-hole-donating ability of this solvent, which results in the formation of uniquely strong solvent-(metal complex) halogen bonding. The strength of the halogen bonding is attenuated by the introduction of additional halogen atoms in the organometallic species owing to the competitive formation of more favourable intermolecular complex-complex halogen bonding. The exceptional solvation properties of diiodomethane and its inertness towards organometallic species make this solvent a good candidate for NMR studies, in particular, for the acquisition of spectra of insensitive spins.
The isocyanide trans‐[PdBr2(CNC6H4‐4‐X′)2] (X′=Br, I) and nitrile trans‐[PtX2(NCC6H4‐4‐X′)2] (X/X′=Cl/Cl, Cl/Br, Br/Cl, Br/Br) complexes exhibit similar structural motif in the solid state, which is determined by hitherto unreported four‐center nodes formed by cyclic halogen bonding. Each node is built up by four Type II C−X′⋅⋅⋅X−M halogen‐bonding contacts and include one Type I M−X⋅⋅⋅X−M interaction, thus giving the rhombic‐like structure. These nodes serve as supramolecular synthons to form 2D layers or double chains of molecules linked by a halogen bond. Results of DFT calculations indicate that all contacts within the nodes are typical noncovalent interactions with the estimated strengths in the range 0.6–2.9 kcal mol−1.
Cobalt(II)-pyridinedicarboxamide-co-polydimethylsiloxane (Co-Py-PDMSs) and cobalt(II)-bipyridinedicarboxamide-co-polydimethylsiloxane (Co-Bipy-PDMSs) polymer−metal complexes were prepared by complexation between Py-PDMSs or Bipy-PDMSs ligands and cobalt(II); the metal content in these complexes varied from 0.09 to 2.41 wt %. The Co II binding patterns (the Co−N Py and Co−O coordination in Co-Py-PDMSs and Co−N Bipy in Co-Bipy-PDMSs) were established by UV−vis and IR methods and by comparison with model Co II complexes exhibiting relevant O,N,O-and N,N-coordination environments, respectively. The mechanical properties of the polymer−metal complexes were controlled by the coordination of Py-PDMSs or Bipy-PDMSs to Co II at various metal-toligand molar ratios (1:(1−6)) and by the variation of the polydimethylsiloxane unit length (M n : 850−900, 5000, or 25 000 g•mol −1 ). Utilization of the chelated Py-PDMSs and Bipy-PDMSs polymer ligands, which are capable of tri-or bidentate binding of Co II , led to (2−4)-fold increases in tensile strength (up to 1.75 MPa) and much higher elongation at break ((2−3)-fold increase up to 2100%) compared with the previously reported Co II -based polymer− ligand systems featuring monodentate ligation entities. Changing the main-chain ligand from Py-PDMSs to Bipy-PDMSs led to an increase in tensile strength of (2−4)-fold in comparison with Py-PDMS and a lower hysteresis (4%). The room temperature selfhealing efficiency was up to 96% for Co-Py-PDMSs and 40% for Co-Bipy-PDMSs, as measured for a polydimethylsiloxane unit with M n = 25 000 g•mol −1 .
Organometallic blue
fluorescent Zn(II) Schiff base complexes are
synthesized and explored computationally in order to use them in organic
electroluminescent heterostructures. Characterization of these pyrazolone-based
azomethine–zinc complexes was accomplished by various physicochemical
techniques to get insight into their applicability as an active layer
in light-emitting diodes. All the complexes demonstrate high thermal
stability and remarkable photoluminescence both in solution and in
the solid state with maximum in the blue region. Quantum chemical
calculations of the first exited electronic state and vertical singlet–singlet
electronic transitions by means of time-dependent density functional
theory calculations and results show that the origin of the luminescence
for the target complexes refers to the intraligand charge transfer
within the Schiff bases. The constructed light-emitting diodes demonstrate
low input voltage (3.2–4.0 V), brightness at a level of 4300–11,600
Cd m–2, and external quantum efficiency of up to
3.2%, which is a good value for purely fluorescent organic light-emitting
diodes.
Two isomorphous series
including the adducts trans-[PdI2(CNC6H4-4-X)2]·2I2 [(1–3)·2I2; X = Cl 1, Br 2, I 3] and
the complexes cis-[PdCl2(CNC6H4-4-X)(PPh3)] (4–6; X = Cl 4, Br 5, I 6) were characterized by X-ray crystallography. Inspection of the
X-ray diffraction data allowed the identification of halogen-bonding
C–X···I–I in (1–3)·2I2 and C–X···Cl–[Pd]
in 4–6 thus providing a rare example
of the triple Cl/Br/I exchange of σ-hole donating halogens.
In accord with the conducted theoretical considerations, the strength
of these XBs are in the range of 0.9–2.8 kcal/mol, and these
contacts are of a noncovalent nature. The calculated maximum electrostatic
potentials on the σ-hole donating X centers of CNC6H4-4-X on the 0.001 au molecular surfaces for both (1–3)·2I2 and 4–6 series are increased along with the decrease
of relative XB lengths. These data are consistent with Politzer and
co-workers conclusions that are based exclusively on theoretical ground.
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