Near-infrared emitting copper(I) complexes with a pyrazolylpyrimidine ligand: exploring relaxation pathways.

Mononuclear copper(I) complexes [CuL2]I (1), [CuL2]2[Cu2I4]·2MeCN (2) and [CuL2]PF6 (3) with a new chelating pyrazolylpyrimidine ligand, 2-(3,5-dimethyl-1H-pyrazol-1-yl)-4,6-diphenylpyrimidine (L), were synthesized. In the structures of complex cations [CuL2]+, Cu+ ions coordinate two L molecules (N,N-chelating coordination). Extended π-systems of the L molecules in [CuL2]+ favor the formation of paired π-π stacking intramolecular interactions between the pyrimidine and phenyl rings leading to significant distortions of tetrahedral coordination cores, CuN4. The free ligand L demonstrates dual excitation wavelength dependent luminescence in the UV and violet regions, which is attributed to S1 → S0 fluorescence and T1 → S0 phosphorescence with intraligand charge transfer character. The complexes 1-3 demonstrate T1 → S0 phosphorescence in the near-infrared region. Theoretical investigations point to its ligand-to-metal charge transfer (LMCT) origin. Large Stokes shifts of emission (ca. 200 nm) are the result of notable planarizations of CuN4 cores in the T1 state as compared to the S0 state. Spin-orbit coupling computations revealed that the most effective intersystem crossing channels for [CuL2]+ appear in high-lying excited states, while the S1 → T1 transition is unfavourable according to El-Sayed's rule and the energy gap law. Electron-vibration coupling calculations showed that the C-C and C-N stretching vibrations of the pyrimidine and phenyl moieties, the asymmetric Cu-N stretching vibrations and the wagging motions of phenyl rings contribute the most to the non-radiative deactivation of L and [CuL2]+.

Structures and optical properties of two phases of SrMgF4.

SrMgF4 has an extremely large bandgap Eg of 12.50 eV as obtained from reflection dispersion. The symmetry of this crystal is monoclinic P21 at room temperature and transforms to the orthorhombic Cmc21 phase near 478 K as the temperature increases. The acentric character of the low-temperature (LT) phase is confirmed by pyroelectric luminescence at T < 440 K. The fundamental absorption edge of the LT phase is located at 122 nm (10.15 eV). A considerable difference between the absorption edge and bandgap Eg is due to the strong exciton absorption. The first-principles electronic structure, refractive indices, nonlinear susceptibility and polarizability were calculated for both LT and high-temperature (HT) phases. Band-to-band transitions are direct for the LT phase but indirect for HT. In spite of relatively low birefringence (∼0.017) and nonlinear susceptibility (∼0.044 pm V(-1), an order lower than that in KDP), SrMgF4 crystals are considered promising for nonlinear optics thanks to their transparency far in the vacuum ultraviolet spectral region.

Syntheses, structures, and electrochemical properties of inclusion compounds of cucurbit[8]uril with cobalt(III) and nickel(II) complexes.

Inclusion compounds of a macrocyclic cavitand cucurbit[8]uril (CB[8]) with cobalt(III) and nickel(II) complexes of 1,3-diaminopropane (tn) and 1,3-diamino-2-propanol (tmOH) { trans-[Co(tn) 2Cl 2]@CB[8]}Cl.14H 2O ( 1), { trans-[Co(tmOH)(tmO)]@CB[8]}Cl 2.22H 2O ( 2), and { trans-[Ni(tmOH) 2]@CB[8]}Cl 2.22H 2O ( 3) were synthesized and characterized by X-ray single crystal analysis, IR spectroscopy, ESI-MS, and by solid-state stripping voltammetry. The encapsulation of trans-[Co(tn) 2Cl 2] (+) within the cavity of CB[8] stabilizes the complex toward ligand substitution reactions in aqueous solution. The electrochemical study demonstrates that CB[8] prefers the oxidized species in trans-[Co(tn) 2Cl 2] (+)/ trans-[Co(tn) 2Cl 2] (0) and trans-[Co(tmO)(tmOH) 2] (2+)/ trans-[Co(tmO)(tmOH) 2] (+) redox couples, but stabilizes the reduced form trans-[Ni(tmOH) 2] (2+) against the oxidized species. The reversibility of voltammogram shapes evidence that for the inclusion compounds 1- 3 electron transfer reactions proceed within the cavity of the host.

Jørgensen complex within a molecular container: selective encapsulation of trans-[Co(en)2Cl2]+ into cucurbit[8]uril and influence of inclusion on guest's properties.

The unprecedented selective encapsulation of trans-[Co(en)2Cl2]+ from the mixture of trans and cis isomers into the cavity of macrocyclic cavitand cucurbit[8]uril (C48H48N32O16, CB[8]) leads to the inclusion compound {trans-[Co(en)2Cl2]@CB[8]}Cl.17H2O (1). Single-crystal X-ray analysis, 1H NMR, and ESI-MS spectra confirm the formation of host-guest complex 1 in both solid state and solution. The geometry of the complex cation alters significantly upon inclusion, which causes appreciable hypsochromic shifts of the absorption bands of the guest complex. According to TGA data, inclusion of trans-[Co(en)2Cl2]+ dramatically stabilizes the complex toward thermal decomposition. Encapsulation of trans-[Co(en)2Cl2]+ into the CB[8] cavity also increases the stability of the metal complex toward isomerization into the cis form. The supramolecular adduct {cis-[Co(en)2(H2O)2](CB[8])6}Cl3.ca109.5H2O (2) was isolated only after prolonged heating of an aqueous solution of 1 at 120 degrees C in an evacuated tube; it was characterized by X-ray crystallography, IR, and elemental analysis.

V4S9Br4: a novel high-spin vanadium cluster thiobromide with square-planar metal core.

The novel vanadium thiobromide, V4S9Br4, with a square-planar metal cluster core was synthesized and characterized by single-crystal X-ray diffraction, measurements of magnetic properties and the heat capacity, and DFT calculations of the electronic structure. At the room temperature, the compound displays paramagnetic properties with an independent spin on each V atom and with a weak exchange constant (J approximately 10 cm(-1)). The paramagnetic state is transformed into a low-spin state (AF-type ordering) at low temperatures. This change is accompanied by a heat-capacity anomaly. The observed magnetic and heat-capacity anomalies can be explained by the thermal excitation of electrons on the closely spaced molecular energy levels in the presence of the Jahn-Teller effect.

Synthesis and reactivity of W3Te74+ clusters and chalcogen exchange in the M3Q7 (M = Mo, W; Q = S, Se, Te) cluster family.

Heating WTe(2), Te, and Br(2) at 390 degrees C followed by extraction with KCN gives [W(3)Te(7)(CN)(6)](2-). Crystal structures of double salts Cs(3.5)K{[W(3)Te(7)(CN)(6)]Br}Br(1.5).4.5H(2)O (1), Cs(2)K(4){[W(3)Te(7)(CN)(6)](2)Cl}Cl.5H(2)O (2), and (Ph(4)P)(3){[W(3)Te(7)(CN)(6)]Br}.H(2)O (3) reveal short Te(2)...X (X = Cl, Br) contacts. Reaction of polymeric Mo(3)Se(7)Br(4) with KNCSe melt gives [Mo(3)Se(7)(CN)(6)](2-). Reactions of polymeric Mo(3)S(7)Br(4) and Mo(3)Te(7)I(4) with KNCSe melt (200-220 degrees C) all give as final product [Mo(3)Se(7)(CN)(6)](2)(-) via intermediate formation of [Mo(3)S(4)Se(3)(CN)(6)](2-)/[Mo(3)SSe(6)(CN)(6)](2-) and of [Mo(3)Te(4)Se(3)(CN)(6)](2-), respectively, as was shown by ESI-MS. (NH(4))(1.5)K(3){[Mo(3)Se(7)(CN)(6)]I}I(1.5).4.5H(2)O (4) was isolated and structurally characterized. Reactions of W(3)Q(7)Br(4) (Q = S, Se) with KNCSe lead to [W(3)Q(4)(CN)(9)](5-). Heating W(3)Te(7)Br(4) in KCNSe melt gives a complicated mixture of W(3)Q(7) and W(3)Q(4) derivatives, as was shown by ESI-MS, from which E(3)[W(3)(mu(3)-Te)(mu-TeSe)(3)(CN)(6)]Br.6H(2)O (5) and K(5)[W(3)(mu(3)-Te)(mu-Se)(3)(CN)(9)] (6) were isolated. X-ray analysis of 5 reveals the presence of a new TeSe(2-) ligand. The complexes were characterized by IR, Raman, electronic, and (77)Se and (125)Te NMR spectra and by ESI mass spectrometry.