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Influence of a Naphthaldiimide Substituent at the Diimine Ligand on the Photophysics and Reverse Saturable Absorption of Pt II Diimine Complexes and Cationic Ir III Complexes
Author(s) -
Liu Rui,
Dandu Naveen,
McCleese Christopher,
Li Yuhao,
Lu Taotao,
Li Hui,
Yost Dillon,
Wang Chengzhe,
Kilina Svetlana,
Burda Clemens,
Sun Wenfang
Publication year - 2015
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201500882
Subject(s) - chemistry , diimine , ligand (biochemistry) , photochemistry , cationic polymerization , substituent , phosphorescence , ultrafast laser spectroscopy , excited state , crystallography , absorption (acoustics) , singlet state , triplet state , quantum yield , stereochemistry , fluorescence , polymer chemistry , molecule , spectroscopy , biochemistry , physics , receptor , organic chemistry , quantum mechanics , nuclear physics , acoustics , catalysis
Two Pt II complexes containing benzothiazolylfluorenyl (BTF) acetylide ligands and different diimine (NN) ligands [NN = 1,10‐phenanthroline ( 1 ), 5‐naphthaldiimide–1,10‐phenanthroline ( 2 )] and two heteroleptic cationic Ir III complexes containing the 5‐naphthaldiimide–1,10‐phenanthroline ligand and different phenylpyridine (CN) ligands [CN = 2‐phenylpyridine ( 3 ), 2‐{3‐[7‐(benzothiazol‐2‐yl)fluoren‐2‐yl]phenyl}pyridine ( 4 )] were synthesized and characterized. The influence of naphthaldiimide (NDI) attached to the NN ligands and benzothiazolylfluorene attached to the CN ligands on the photophysical properties of these Pt II /Ir III complexes has been investigated spectroscopically and theoretically. All complexes exhibit ligand‐localized 1 π,π* transitions below 400 nm, and broad and structureless metal‐to‐ligand/ligand‐to‐ligand charge transfer ( 1 MLCT/ 1 LLCT) transitions between 400 and 550 nm. Complexes 1 and 4 show red phosphorescence in toluene solutions at room temperature, where the emitting state is assigned predominantly to the 3 π,π* state for complex 1 and 3 LLCT/ 3 MLCT states for complex 4 . Incorporation of the NDI substituent to the NN ligand completely or partially quenches the emission of complexes 2 – 4 . Complexes 1 – 4 all possess broad singlet transient absorption from 400 to 800 nm, which is ascribed to 1 π,π*/ 1 MLCT/ 1 LLCT states for complex 1 , and to 1 NDI – · for complexes 2 – 4 . The ns transient absorption study reveals that complex 1 exhibits a broad triplet excited‐state absorption from the 3 π,π*/ 3 MLCT states, while complexes 2 – 4 give moderately strong triplet excited‐state absorption from 3 NDI – · . Nonlinear transmission experiments at 532 nm using nanosecond laser pulses demonstrate that these complexes all exhibit strong reverse saturable absorption (RSA) at 532 nm for ns laser pulses. Introduction of the NDI substituent to the NN ligand causes charge transfer to the NDI component, which in turn increases the RSA of the Pt II complex 2 in comparison with that of the Pt II complex 1 ; while attaching the BTF component to the CN ligands enhances the RSA of the Ir III complex 4 in comparison with that of complex 3 .