Martínez-Junquera Mónica, Lalinde Elena, Moreno M Teresa
Departamento de Química-Centro de Síntesis Química de La Rioja, (CISQ), Universidad de La Rioja, 26006 Logroño, Spain.
Inorg Chem. 2023 Jul 31;62(30):11849-11868. doi: 10.1021/acs.inorgchem.3c01196. Epub 2023 Jul 17.
/ Isomerism can be a crucial factor for photophysical properties. Here, we report the synthesis and optical properties of a series of - and -alkynyl/isocyanide cycloplatinated compounds [Pt(CN)(C≡CR)(CNBu)] [R = CH-4-OMe , 3-CHS ; CN = 2-(2,4-difluorophenyl)pyridine (dfppy) (), 4-(2-pyridyl)benzaldehyde (ppy-CHO) ()]. The -forms do not isomerize thermally in MeCN solution to the forms, but upon photochemical irradiation in this medium at 298 K, a variable isomerization to the forms was observed. This behavior is in good agreement with the theoretically calculated energy values. The / configuration, the identity of the cyclometalated, and the alkynyl ligand influence on the absorption and emission properties of the complexes in solution, polystyrene (PS) films, and solid state are reported. All complexes are efficient triplet emitters in all media (except for - and - in CHCl solution at 298 K), with emission wavelengths depending mainly on the cyclometalated ligand in the region 473-490 nm (dfppy), 510-550 (ppy-CHO), and quantum yields (ϕ) ranging from 18.5 to 40.7% in PS films. The combined photophysical data and time-dependent density functional theory calculations (TD-DFT) at the excited-state T geometry reveal triplet excited states of L'LCT (C≡CR → CN)/IL (CN) character with minor MLCT contribution. The dfppy () complexes show a greater tendency to aggregate in rigid media than the ppy-CHO () and the with respect to the , showing red-shifted structureless bands of MMLCT and/or excimer-like nature. Interestingly, and undergo significant changes in the ultraviolet (UV) and emission spectra with Hg ions enabling their use for sensing of Hg ions in solution. This is clearly shown by the hypsochromic shift and substantial decrease of the low-energy absorption band and an increase of the intensity of the emission in the MeCN solution upon the addition of a solution of Hg(ClO) (1:5 molar ratio). Job's plot analysis estimated a 1:1 stoichiometry in the complexation mode of Hg by . The binding constant (log ) calculated for this system from absorption titration data resulted to be 2.56, and the limit of the detection (LOD) was 6.54 × 10 M.
异构现象可能是影响光物理性质的关键因素。在此，我们报告了一系列α-和β-炔基/异腈环金属铂化合物[Pt(CN)(C≡CR)(CNBu)] [R = CH-4-OMe、3-CHS；CN = 2-(2,4-二氟苯基)吡啶(dfppy) (α)、4-(2-吡啶基)苯甲醛(ppy-CHO) (β)]的合成及光学性质。α-型在乙腈溶液中不会热异构化为β-型，但在298 K下于该介质中进行光化学辐照时，会观察到向β-型的可变异构化。这种行为与理论计算的能量值高度吻合。报告了α/β构型、环金属化配体的身份以及炔基配体对配合物在溶液、聚苯乙烯(PS)薄膜和固态中的吸收和发射性质的影响。所有配合物在所有介质中（298 K下的CHCl溶液中的α-和β-型除外）都是有效的三线态发射体，发射波长主要取决于环金属化配体，在473 - 490 nm区域（dfppy）、510 - 550（ppy-CHO），在PS薄膜中的量子产率(ϕ)范围为18.5%至40.7%。结合光物理数据和激发态T几何结构下的含时密度泛函理论计算(TD-DFT)揭示了具有少量MLCT贡献的L'LCT（C≡CR → CN）/IL（CN）特征的三线态激发态。与ppy-CHO（β）以及α相对于β而言，dfppy（α）配合物在刚性介质中表现出更大的聚集倾向，呈现出红移的无结构带，具有MMLCT和/或准分子样性质。有趣的是，α和β在紫外(UV)和发射光谱上会随着Hg离子发生显著变化，这使得它们可用于溶液中Hg离子的传感。在加入Hg(ClO)溶液（摩尔比1:5）后，乙腈溶液中低能量吸收带的紫移和大幅降低以及发射强度的增加清楚地表明了这一点。Job曲线分析估计Hg与β的络合模式为1:1化学计量比。根据吸收滴定数据计算出该体系的结合常数(log )为2.56，检测限(LOD)为6.54 × 10⁻⁷ M。
