A series of new Pt(II) diimine complexes with different carbazolyl-capped acetylide ligands (Pt-1–Pt-5) were synthesized and characterized. Their photophysical properties were investigated systematically via spectroscopic and theoretical methods. All complexes exhibit ligand-centered 1π,π* transitions in the UV region, and broad, structureless metal-to-ligand charge transfer (1MLCT)/ligand-to-ligand charge transfer (1LLCT) absorption bands in the visible spectral region. All complexes are emissive in solution at room temperature, with the emitting state being tentatively assigned to the 3MLCT/3LLCT states for Pt-1–Pt-4, and the emitting state of Pt-5 exhibiting a switch from the 3π,π* state in high-polarity solvents to the 3MLCT state in low-polarity solvents. Complexes Pt-1–Pt-5 all exhibit moderate triplet transient absorption (TA) from the visible to the NIR region, where reverse saturable absorption (RSA) could occur. The spectroscopic studies and theoretical calculations indicate that the photophysical properties of these Pt complexes can be tuned drastically by the carbazolyl-capped acetylide ligand, which would be useful for rational design of transition-metal complexes with high emission quantum yield, long excited-state lifetime, broadband excited-state absorption, and strong nonlinear transmittance for organic light-emitting and/or broadband nonlinear transmission applications.

•Our work succeeds in synthesizing a series of aza-boron-diquinomethene complexes.•These complexes show high fluorescence quantum yields and thermal stability.•Optical, electrochemical properties and DFT calculations were investigated.•These complexes are expected to be promising light-emitting materials in OLEDs.A series of aza-boron-diquinomethene (aza-BODIQU) complexes with different aryl-substituents (B1–B6) were synthesized and characterized. Their photophysical properties were investigated systematically via spectroscopic and theoretical methods. All complexes exhibit strong 1π–π* absorption bands and intense fluorescent emission bands in the visible spectral region at room temperature. The fluorescence spectra in solution show the mirror image features of the S0→S1 absorption bands, which can be assigned to the 1π–π*/1ICT (intramolecular charge transfer) emitting states. Except for B6, all complexes exhibit high photoluminescence quantum yields (ΦPL = 0.47–0.93). The spectroscopic studies and theoretical calculations indicate that the photophysical properties of these aza-BODIQUs can be tuned by the appended aryl-substituents, which would be useful for rational design of boron–fluorine complexes with high emission quantum yield for organic light-emitting applications.A series of aza-boron-diquinomethene complexes B1–B6 exhibit sharp absorption and emission bands with high photoluminescence quantum yields (ΦPL = 0.47–0.93).

A rapid, simple and real-time colorimetric assay for detecting phosphate anions (PO43−) in aqueous solution was developed. The method was based on a novel functionalized gold nanoparticles (MPTP-Zn-AuNPs), which was synthesized by the ligand-exchange reaction of 4′-(4-mercaptophenyl)-2,2′:6′,2″-terpyridine zinc(II) complex (MPTP-Zn) with citrate-stabilized aqueous AuNPs. The strong coordination between MPTP-Zn-AuNPs and PO43− anion gave rise to a color change from wine-red to blue-gray that was discernible by the naked eye and an easily measurable alteration in the absorption spectrum of the particles in aqueous solution. And the new technique exhibited the high selectivity for PO43− over 11 other anions and could be used to determine PO43− with a detection limit of 11 ppm.Highlights► A rapid, simple and real-time colorimetric assay for detecting PO43− was developed. ► The present method was based on a novel functionalized gold nanoparticles. ► The new technique exhibited high selectivity for PO43− with a detection limit of 11 ppm.

The photophysical properties of a series of 4,4′-diethynylazobenzene derivatives terminally capped with substituted aromatic rings (1a: R = phenyl; 1b: R = 4-(diphenylamino)phenyl; 1c: R = 4-(9H-carbazol-9-yl)phenyl; 1d: R = 9H-fluoren-2-yl; 1e: R = biphenyl-4-yl; 1f: R = naphthalen-2-yl) were systematically investigated. All compounds exhibit strong 1π,π* absorption bands in the UV region; and a broad, structureless charge-transfer band/shoulder in the visible region (except for 1a), which systematically red-shifts when electron-donating substituents are introduced to the terminal phenyl rings, but blue-shifts when π-conjugation of the terminal aromatic ring increases. All compounds are emissive in solution at room temperature and at 77 K. When excited at the low-energy absorption band, the compounds emit fluorescence between 369 and 419 nm, which can be attributed to 1π,π*/1ICT (intramolecular charge transfer) state. Density functional theory (DFT) calculations on 1a–1f in gas phase were also performed to gain insight into the nature of the ground electronic state and the low-lying excited electronic states. 1d–1f exhibit strong triplet transient absorption band(s) in the visible spectral region, which are mainly attributed to the 3π,π* state. Reverse saturable absorption (RSA) of these compounds was demonstrated at 532 nm using ns laser pulses. The degree of RSA follows this trend: 1b > 1c ≈ 1a > 1e >1f > 1d, which is mainly determined by the ratio of the triplet excited-state absorption cross-section to that of the ground-state and the triplet excited-state quantum yield.Graphical abstractThe photophysical properties, nonlinear absorption characteristics and the influence of the substituted aromatic rings on the nature of excited states of a series of 4,4′-diethynylazobenzene derivatives (1a–1f) were systematically investigated. All compounds exhibit reverse saturable absorption at 532 nm and could potentially be used as nonlinear absorbing materials.Highlights► Photophysics of 4,4′-diethynylazobenzene derivatives was systematically investigated. ► Excited state properties can be tuned by alternation of the terminal substituents. ► Compounds exhibit varied reverse saturable absorption at 532 nm for ns laser pulses.

A series of new Pt(II) diimine complexes with different carbazolyl-capped acetylide ligands (Pt-1–Pt-5) were synthesized and characterized. Their photophysical properties were investigated systematically via spectroscopic and theoretical methods. All complexes exhibit ligand-centered 1π,π* transitions in the UV region, and broad, structureless metal-to-ligand charge transfer (1MLCT)/ligand-to-ligand charge transfer (1LLCT) absorption bands in the visible spectral region. All complexes are emissive in solution at room temperature, with the emitting state being tentatively assigned to the 3MLCT/3LLCT states for Pt-1–Pt-4, and the emitting state of Pt-5 exhibiting a switch from the 3π,π* state in high-polarity solvents to the 3MLCT state in low-polarity solvents. Complexes Pt-1–Pt-5 all exhibit moderate triplet transient absorption (TA) from the visible to the NIR region, where reverse saturable absorption (RSA) could occur. The spectroscopic studies and theoretical calculations indicate that the photophysical properties of these Pt complexes can be tuned drastically by the carbazolyl-capped acetylide ligand, which would be useful for rational design of transition-metal complexes with high emission quantum yield, long excited-state lifetime, broadband excited-state absorption, and strong nonlinear transmittance for organic light-emitting and/or broadband nonlinear transmission applications.