Synthesis And Properties Of Platinum(Ⅱ) Complexes With Imine Phosphine Oxide/Phosphine Ligands

In this paper,using bulky imine phosphine oxide and imine phosphine compounds as ancillary ligands,a series of neutral mononuclear platinum（II）complexes,neutral dinuclear platinum（II）complexes and ionic mononuclear platinum（II）complexes were synthesized.Their structures were confirmed by NMR,elemental analysis and single crystal X-ray diffraction,and their luminescence properties were deeply studied.Furthermore,the simulated UV-Vis absorption spectra of the complexes were obtained by time-dependent density functional theory（TD-DFT）calculation.The main contents are as follows:（1）Using benzimidazole phosphine oxides derivatives（OL1-OL4）and benzimidazole phosphine derivatives（L1-L4）as ancillary ligands,eight neutral mononuclear cycloplatinated（II）complexes based on 2-phenylbenzothiazole（bt）（Pt1OL1-Pt1OL4 and Pt1L1-Pt1L4）and eight neutral mononuclear cycloplatinated（II）complexes based on 1-phenylisoquinoline（piq）（Pt2OL1-Pt2OL4 and Pt2L1-Pt2L4）were obtained.The crystal structures of these complexes display distorted square planar geometries around Pt（II）centers,without obvious intermolecularπ-πand Pt-Pt interactions.These complexes based on bt all exhibit excellent monomeric emissions with the highest luminescent quantum yield of 65%for Pt1OL1 in powder.The emission colors of the complexes based on piq can be finely tuned in the range600-645 nm by changing the ancillary ligands.The complexes Pt2OL1-Pt2OL4 with pure red emissions show moderate luminescent quantum yields of 18%-23%in dichloromethane at 298K,which may have the potential application as optical communication materials.（2）Using triazole phosphine oxide derivatives（OL5-OL7）and triazole phosphine derivatives（L5-L7）as ancillary ligands,six neutral cycloplatinated（II）complexes based on bt（Pt1OL5-Pt1OL7 and Pt1L5-Pt1L7）and six neutral cycloplatinated（II）complexes based on piq（Pt2OL5-Pt2OL7 and Pt2L5-Pt2L7）have been synthesized.Crystal structure analysis indicate that platinum（II）complexes（Pt1OL5-Pt1OL7 and Pt2OL5-Pt2OL7）based on OL5-OL7 ancillary ligands are neutral binuclear platinum complexes with obvious intramolecular Pt-Pt interactions.Based on L5-L7 ancillary ligands,platinum（II）complexes Pt1L5-Pt1L7 and Pt2L5-Pt2L7 form neutral mononuclear platinum complexes with distorted square planar geometries around Pt（II）centers.There are no obvious intermolecularπ-πand Pt-Pt interactions.The bt-based platinum（II）complexes show excellent yellow emission in powder,and the luminescent quantum yield of Pt1OL6 is up to 67%.The piq-based platinum（II）complexes Pt2OL5-Pt2OL7 display pure red emission with quantum yields of15%～20%in dichloromethane at 298K.（3）Using phenyl-substituted benzimidazole phosphine derivatives（L8-L11）as ancillary ligands,bt and piq as cyclometalating ligands,tetrafluoroborate（BF₄^-）and hexafluoroantimonate（Sb F₆^-）as counter anions,sixteen ionic luminescent cycloplatinated（II）complexes（bt series:Pt1L8-BF₄～Pt1L11-BF₄and Pt1L8-Sb F₆～Pt1L11-Sb F₆;piqseries:Pt2L8-BF₄～Pt2L11-BF₄and Pt2L8-Sb F₆～Pt2L11-Sb F₆）were obtained.In these complexes,Pt（II）centers were chelated with the ancillary ligands（L8-L11）in a N^P manner,forming a twisted square planar geometries.There are no obvious intermolecularπ-πand Pt-Pt interactions.The Sb F₆^-and BF₄^-anions can form C-H…F hydrogen bonds with the aryl protons of adjacent molecules.The weak hydrogen bonds can solidify the conformation and suppress molecular vibrations,which are beneficial to obtain platinum（II）complexes with superior luminescent properties.Eight complexes Pt1L8-BF₄～Pt1L11-BF₄and Pt1L8-Sb F₆～Pt1L11-Sb F₆exhibit excellent yellow emissions in powder with the highest luminescent quantum yield up to 59%.Eight complexes Pt2L8-BF₄～Pt2L11-BF₄and Pt2L8-Sb F₆～Pt2L11-Sb F₆exhibit good red emissions with moderate luminescence quantum yields of 16%～27%in dichloromethane and in powder at 298K.The low-energy absorptions（>350 nm）mainly originate from the mixed metal-to-ligand charge transfer（MLCT）transitions,intra-ligand charge transfer（ILCT）transition and ligand-to-ligand charge transfer（LLCT）transitions.The solid-state emission spectra of all the complexes at 77K showed highly structured vibronic bands without obvious rigidochromic shift compared to that at 298K.The structured emissions together with their microsecond radiative lifetimes indicate that the phosphorescence emissions of all the complexes are mainly the ³LC character with some ³MLCT feature.