N-杂环亚丙二烯基钯(Ⅱ)离子化合物在非极性溶剂中的自组装行为和磷光性质  

Self-assembly and phosphorescence of ionic Pd(Ⅱ)N-heterocyclic allenylidene complexes in nonpolar solvents

作　　者：周宁 邹超 陆为 Ning Zhou;Chao Zou;Wei Lu(Department of Chemistry,Southern University of Science and Technology,Shenzhen 518055,China)

机构地区：[1]南方科技大学化学系,深圳518055

出　　处：《科学通报》2021年第25期3342-3351,共10页Chinese Science Bulletin

基　　金：国家自然科学基金(21873044,21901109);深圳市科技创新委员会项目(JCYJ2017081710471517);广东省基础与应用基础研究重大项目(2019B030302009)资助。

摘　　要：相较于报道较多的磷光Pt(Ⅱ)化合物,同样具有d8电子构型平面四边形配位的Pd(Ⅱ)化合物在室温溶液中的磷光报道较少.尤其因为其较低的d-d轨道能级,使得金属Pd(Ⅱ)参与的磷光发光机制研究非常少见.而利用亲金属Pd(Ⅱ)···Pd(Ⅱ)弱作用力构建自组装聚集体是实现室温溶液中Pd(Ⅱ)化合物磷光发射的一个有效渠道.本文通过使用N-杂环亚丙二烯基前体2-乙炔基-1,3-二甲基-咪唑六氟磷酸盐(1·PF6)与含有烷基长链取代的钳形C^N^N-Pd(Ⅱ)Cl(HC^N^N=6-苯基-4-(3,4,5-三(十二烷氧基)苯基)-2,2′-联吡啶)化合物2,在氧化银存在下利用转金属反应合成了阳离子型亚丙二烯基Pd(Ⅱ)化合物3·PF6,并通过核磁、高分辨质谱、红外等表征化合物的组成与结构.化合物3·PF6溶解于二氯甲烷稀溶液中呈现出微弱的光致发光现象(量子产率<1%,寿命为17 ns).而使用二氯甲烷/环己烷的混合溶剂体系,随着溶剂极性降低,紫外-可见吸收光谱中低能量特征峰的出现以及1H NMR峰宽化等现象预示着化合物3·PF6逐渐聚集,并伴随着不断增强且红移的光致发光,在纯环己烷溶液中可以实现最大发射在612 nm且量子产率达到35.4%的光致发光.利用变温紫外-可见吸收光谱考察504 nm处的低能量特征吸收峰强度随温度的变化及数据拟合,表明化合物3·PF6在非极性溶剂(如甲基环己烷、十氢萘)中的自组装行为符合成核-生长模型特征.In sharp contrast with the rich phosphorescent Pt(Ⅱ)complexes reported in the literatures,phosphorescent Pd(Ⅱ)complexes in room temperature solutions are scarce,in spite of having the same d8 electronic configuration and squareplanar coordination mode.Due to their low-lying d-d transition state,phosphorescence origin of the Pd(Ⅱ)complexes are usually ligand-based,rather than much metal participation.Recently,it has been proved to be an effective strategy to construct self-assembled aggregates via metallophilic Pd···Pd interactions for Pd(Ⅱ)complexes to achieve metal-metal-toligand charge transfer(MMLCT)and corresponding phosphorescent emission in room temperature fluid state.Herein,a cationic N-heterocyclic allenylidene(NHA)Pd(Ⅱ)complex 3·PF6 has been synthesized via a facile two-step transmetalation reaction of NHA precursor 2-ethynyl-1,3-dimethyl-1 H-imidazol-3-ium hexafluorophosphate(1·PF6)and a pincer type[(C^N^N)Pd Cl](HC^N^N=6-phenyl-4-(3,4,5-tris(dodecyloxy)phenyl)-2,2′-bipyridine)2 with long alkyl chains in the presence of excessive amount of Ag2 O.It is stable towards air,moisture and common organic solvents.The purity of the cationic NHA Pd(Ⅱ)complex 3·PF6 was characterized via NMR,HR-MS.And IR spectra revealed its resonance structure between zwitterionic acetylide and N-heterocyclic allenylidene to some extent.Solid state complex 3·PF6 showed orange emission with microsecond lifetime at both room temperature and 77 K.Temperature-dependent PXRD and TGA/DSC analysis demonstrated the changes of complex 3·PF6 from an amorphous phase to a stable crystalline one upon raising the temperature.Due to the lipophilic property of the long alkyl chains,ionic complex 3·PF6 can be soluble in both polar(such as dimethyl sulfoxide(DMSO),CH3 CN,and dichloromethane)and nonpolar(such as cyclohexane,methylcyclohexane,and decalin)organic solvent,despite its ionic nature.Complex 3·PF6 in degassed dilute DCM solution showed rather weak photoluminescence with peak maximum at 562 nm(QY<1%,τ:17 ns).By in

关 键 词：钯 磷光 亲金属相互作用 自组装 成核生长 

分 类 号：O641.4[理学—物理化学]