求翻译 化学类文献

求翻译 化学类文献
Design and synthesis: 6-Phenyl-2,2’-bipyridine (HC^N^N)
and 1,3-di(pyridin-2-yl)benzene (HN^C^N) represent the
basic designs of common p-conjugated tridentate cyclometalating
ligands for cyclometalated PtII systems. However,
these well-established ligand systems are difficult to be further
modified or functionalised. The presence of a 1-pyrazolyl-
NH on the new cyclometalating ligand, HL1, enables its
easy functionalisation by nucleophilic substitution.[14] We
demonstrated this by direct alkylation of the 1-pyrazolyl-
NH site on HL1 with 1,5-dibromopentane to generate HL2
in good yield. Further nucleophilic substitution of the terminal
alkyl bromide on HL2 by PPh3 yielded the triphenylphosphonium-
functionalised cyclometalating ligand, triphenyl{
5-[3-(6-phenylpyridin-2-yl)-1H-pyrazol-1-yl]pentyl}phosphonium
bromide (HL3) (Scheme 1). The chloride salt of
HL3 was obtained by simple metathesis. The corresponding
cyclometalated PtII–chloride complex, [Pt(L3)Cl]+, was obtained
in good yield by direct metalation of HL3 (chloride
salt) with K2PtCl4 in glacial acetic acid. All of the new ligands
and the cycloplatinated complex reported have been
fully characterised by 1H NMR spectroscopy and mass spectrometry.
Linear photophysical studies: Electronic transition spectra
of [Pt(L3)Cl]+ in various solvents are shown in Figure 1A.
Spectroscopic properties of the complex show strong resemblances
to its related [Pt(L1)Cl] complex. The UV-visible
region is dominated by intense absorption bands at around
275–375 nm with extinction coefficients (e) in the order of
104 dm3mol\21cm\21 and a less intense band at around 380–
410 nm with e in the order of 103 dm3mol\21cm\21. With reference
to previous spectroscopic studies of the analogous [Pt-
ACHTUNGTRENUNG(C^N^N)Cl] and [Pt(L1)Cl] complexes, absorption bands at
275–375 nm are attributed to intraligand (p(L)!p*(L))
transitions, whereas the lower energy absorption band at
380–410 nm is assigned the spin-allowed dp(Pt)!p*(L)
metal-to-ligand charge-transfer (1MLCT) transition. The
lmax of the lower energy band is solvent dependent and
shifts from 387 nm in methanol to 393 nm in chloroform.
This supports the assignment that the absorption band is
from a charge-transfer transition.