Trinuclear Copper(I) and Silver(I) Adducts of 4‑Chloro-3,5-bis(trifluoromethyl)pyrazolate and 4‑Bromo-3,5-bis(trifluoromethyl)pyrazolate

Syntheses,
structural, and photoluminescence properties of {[4-X-3,5-(CF3)2Pz]­M}3 (X = Cl or Br, M = Cu or Ag)
containing a heavier halide at the pyrazolyl ring 4-positions are
reported. The Cu2O and Ag2O react with [4-Cl-3,5-(CF3)2Pz]H or [4-Br-3,5-(CF3)2Pz]H to form the corresponding metal pyrazolates, which are trinuclear
adducts of the type {[4-X-3,5-(CF3)2Pz]­M}3 with a nine-membered M3N6 metallacyclic
core. They also feature relatively short M···Cl or
M···Br intertrimer separations (∼ 3.6 Å)
leading to supramolecular aggregates in the solid state. Distinct
from the 4-H analogues {[3,5-(CF3)2Pz]­M}3, none of the four complexes described herein exhibits short
intertrimer metal–metal interactions (as closest such M···M
separations are at a distance greater than 5.0 Å). The {[4-X-3,5-(CF3)2Pz]­M}3 adducts exhibit bright photoluminescence
even at room temperature. The photophysical data suggest that the
{[4-X-3,5-(CF3)2Pz]­Cu}3 complexes
emit from an associative excited state, and the drastic Stokes shift
suggests a significant change to the ground state structure of the
trinuclear moiety and/or intermolecular interactions upon photoexcitation.
The {[4-X-3,5-(CF3)2Pz]­Ag}3 complexes
emit from a ligand-centered excited state affected by silver and the
heavier halogens. Thin films of {[4-X-3,5-(CF3)2Pz]­Cu}3 trimers are promising for volatile organic compound
(VOC) sensor applications as they exhibit luminescence color change
upon exposure to vapors of benzene and its alkylated derivatives.

本文报道了吡唑环4-位带有重卤原子的{[4-X-3,5-双(三氟甲基)吡唑基]M}3（X=Cl或Br，M=Cu或Ag）的合成、结构及光致发光性能。氧化亚铜（Cu₂O）与氧化银（Ag₂O）可分别与[4-氯-3,5-双(三氟甲基)吡唑基]H或[4-溴-3,5-双(三氟甲基)吡唑基]H反应，得到相应的金属吡唑配合物，该类配合物为{[4-X-3,5-双(三氟甲基)吡唑基]M}3型三核加合物，具有九元M₃N₆金属环核心。这类配合物还存在较短的三聚体间M···Cl或M···Br间距（约3.6 Å），在固态下形成超分子聚集体。与4-位未取代的类似物{[3,5-双(三氟甲基)吡唑基]M}3不同，本文所述的四种配合物均未表现出较短的分子间金属-金属相互作用（此类M···M的最短间距均大于5.0 Å）。{[4-X-3,5-双(三氟甲基)吡唑基]M}3加合物在室温下即可展现出明亮的光致发光。光物理数据表明，{[4-X-3,5-双(三氟甲基)吡唑基]Cu}3配合物的发射源自缔合激发态，其大幅的斯托克斯位移（Stokes shift）说明，在光激发过程中，三核单元的基态结构以及/或者分子间相互作用发生了显著变化。{[4-X-3,5-双(三氟甲基)吡唑基]Ag}3配合物的发射源自受银原子与重卤原子影响的配体中心激发态。{[4-X-3,5-双(三氟甲基)吡唑基]Cu}3三聚体的薄膜在暴露于苯及其烷基衍生物蒸气时，会发生发光颜色变化，因此在挥发性有机化合物（volatile organic compound, VOC）传感应用中具有良好前景。