Search

Five bismuth(III)-organic phases that consist of supramolecular assemblies of Bi-2,6-pyridinedicarboxylate structural units and substituted 1,10-phenanthroline molecules (R-Phen; R = H, 5-methyl, 5-chloro, 2,9-dimethyl, and 2,9-dicholoro) were synthesized. All five compounds exhibited solid-state photoluminescence. Whereas the phases containing 2,9-dimethylphenanthroline (Me2Phen) and 2,9-dichlorophenanthroline (Cl2Phen) displayed solely phosphorescence, the structures built from 5-methylphenanthroline and 5-chlorophenanthroline showed exclusively fluorescence. The remaining phase, consisting of phenanthrolinium, exhibited both fluorescence and phosphoresence. It was determined that phosphorescence arises from triplet state emission (T1 → S0) of substituted R-Phen units while fluorescence originates from Bi(III) coordinated pyrdinedicarboxylate ligands. Bismuth induces spin–orbit coupling for triplet state population and additionally acts as a heavy metal attenuator for X-ray luminescence (radioluminescence). The electronic structure was mapped and excitation pathway investigated via density functional theory calculations. Computational findings indicate favorable conditions for triplet energy transfer from donor Bi(III)-organic units to acceptor R-Phen derivatives. It is proposed that for the phosphorescent compounds, strong π–π interactions promote electron transfer, whereas the compounds that exhibit purely fluorescence lack any such π–π interactions and undergo triplet energy transfer. These results provide a useful platform for probing structure–property relationships of luminescent bismuth-organic compounds, and specifically highlights the role of noncovalent interactions in achieving room temperature phosphorescence and radioluminescence. [ABSTRACT FROM AUTHOR]

Perovskite light‐emitting diodes (PeLEDs) are advancing because of their superior external quantum efficiencies (EQEs) and color purity. Still, additional work is needed for blue PeLEDs to achieve the same benchmarks as the other visible colors. This study demonstrates an extremely efficient blue PeLED with a 488 nm peak emission, a maximum luminance of 8600 cd m−2, and a maximum EQE of 12.2% by incorporating the double‐sided ethane‐1,2‐diammonium bromide (EDBr2) ligand salt along with the long‐chain ligand methylphenylammonium chloride (MeCl). The EDBr2 successfully improves the interaction between 2D perovskite layers by reducing the weak van der Waals interaction and creating a Dion–Jacobson (DJ) structure. Whereas the pristine sample (without EDBr2) is inhibited by small stacking number (n) 2D phases with nonradiative recombination regions that diminish the PeLED performance, adding EDBr2 successfully enables better energy transfer from small n phases to larger n phases. As evidenced by photoluminescence (PL), scanning electron microscopy (SEM), and atomic force microscopy (AFM) characterization, EDBr2 improves the morphology by reduction of pinholes and passivation of defects, subsequently improving the efficiencies and operational lifetimes of quasi‐2D blue PeLEDs. [ABSTRACT FROM AUTHOR]

The photochromic compounds trans- and cis-[Ru(tpy)(Mepic)(dmso)](OS[O.sub.2]C[F.sub.3]) [where tpy=2,2':6',2'-terpyridine; Mepic=6-methyl-2-pyridinecarboxylate; dmso=dimethyl sulfoxide] and cis-[Ru(tpy)(Brpic)(dmso)](P[F.sub.6]) [where Brpic=6-bromo-2-pyridinecarboxylate] were prepared and characterized. The methyl group promotes isomerization by hindering rotation of the dmso ligand about the Ru-S bond indicating that rotation is an important vibration for isomerization in photochromic Ru-dmso complexes.

Investigations indicate that dmso isomerization in ruthenium occurs within a strong-field ligand environment. Isomerization in these complexes occurs following format ion of an equilibrated S-bonded excited state.

A new method enables the preparation of cationic silver (I) carbonyl complexes (Ag(CO))+ and (Ag(CO)2)+ as salts of a number of anions having the OTeF5 group. These crystalline compounds are stable under a CO atmosphere or at low temperatures. Manometric and spectroscopic studies of these compounds reveal the absence of Ag to carbon pi-back-bonding, indicating that they belong to a group of nonclassical metal cabonyls. X-ray crystallographic studies help characterize two of the new compounds.

Transient absorption data of [FeII(tpy)(CN)3]− reveals spectroscopic signatures indicative of 3MLCT with a ∼10 ps kinetic component. These data are supported by DFT and TD-DFT calculations, which show that excited state ordering is responsive to the number of cyanide ligands on the complex. [ABSTRACT FROM AUTHOR]

A study was conducted to demonstrate the efficient S --> O isomerization observed in a chelating sulfoxide, which showed evidence for two O-bonded isomers. Examination of the [super 1]H NMR spectra in a C[D.sub.3]OD solvent before, during, and after irradiation shows the presence of two O-bonded complexes that revert to the structurally characterized S-bonded ground state.

The examination of phototriggered excited-state isomerization in osmium-polypyridyl complexes containing ruthenium-dimethyl sulfoxide (DMSO) is done to study the role of ligand-field states in DMSO photochromic complexes. That DMSO isomerization occurs on osmium suggests that this reaction does not require intervention of photoreactive ligand-field states.

Lanthanide ion (LnIII) complexes, [Ln(3Tcbx)2]3+ (LnIII=YbIII, NdIII, ErIII) are isolated with a new pyridine‐bis(carboxamide)‐based ligand with a 2,2′:5′,2′′‐terthiophene pendant (3TCbx), and their resulting photophysical properties are explored. Upon excitation of the complexes at 490 nm, only LnIII emission is observed with efficiencies of 0.29 % at 976 nm for LnIII=YbIII and 0.16 % at 1053 nm for LnIII=NdIII. ErIII emission is observed but weak. Upon excitation at 400 nm, concurrent 1O2 formation is seen, with efficiencies of 11 % for the YbIII and NdIII complexes and 13 % for the ErIII complex. Owing to the concurrent generation of 1O2, as expected, the efficiency of metal‐centered emission decreases to 0.02 % for YbIII and 0.05 % for NdIII. The ability to control 1O2 generation through the excitation wavelength indicates that the incorporation of 2,2′:5′,2′′‐terthiophene results in access to multiple sensitization pathways. These energy pathways are unraveled through transient absorption spectroscopy. [ABSTRACT FROM AUTHOR]

A new pyridine-bis(carboxamide)-based ligand with a bithiophene pendant, 2Tcbx, was synthesized. Its lanthanide ion (LnIII) complexes, [Ln(2Tcbx)2]3+, were isolated and their photophysical properties were explored. Upon excitation at 360 nm, these complexes display emission in the near-infrared (NIR) with efficiencies of 0.69% for LnIII = YbIII, 0.20% for LnIII = NdIII, and 0.01% for LnIII = ErIII, respectively. Concurrent 1O2 formation was seen for all complexes, with efficiencies of 19% for the YbIII complex, 25% for the NdIII complex, and 9% for the ErIII complex. When exciting at a longer wavelength, 435 nm, only LnIII emission was observed and larger efficiencies of LnIII-centered emission were obtained. The lack of 1O2 generation indicates that energy pathways involving different ligand conformations, which were investigated by transient absorption spectroscopy, are involved in the sensitization process, and enable the wavelength-dependent generation of 1O2. [ABSTRACT FROM AUTHOR]

A series of Ru(II)-terpyridine complexes containing electron-donating bidentate ligands are able to effectively photodissociate nitrile ligands using red light. A spectroscopic investigation of these complexes reveal that they follow anti-energy gap law behavior, providing further evidence that population of 3LF excited states is not necessary for photoinduced nitrile dissociation. [ABSTRACT FROM AUTHOR]

The S==O stretching mode in sulfoxides, having a frequency in the 950-1150 cm-1 range, is tested as a structural label via dual-frequency two-dimensional infrared (2DIR) spectroscopy. The properties of this structural reporter are studied in several compounds, including (4,4′-dimethyl-2,2′-bipyridyl)(o-methylsulfinylbenzoate) ruthenium II, [Ru(dmb)2(BzSO)]+, (RuBzSO), octylsulfinylpropionic acid (OSPA), and o- and p-methylsulfinyl-benzoic acid (oMSBA and pMSBA). The mode assignment in the fingerprint region for these compounds is made using a combination of density functional theory calculations and 2DIR and relaxation-assisted 2DIR (RA 2DIR) spectroscopies. The SO stretching mode frequency and IR intensity demonstrate substantial sensitivity to the molecular structure. Multiple cross peaks of the C==O and S==O stretching modes with modes in the fingerprint region (930-1450 cm-1) were recorded. The 2DIR and RA 2DIR spectra focusing at interactions of a high-frequency mode of a ligand with the modes in the fingerprint region provide a spectral fingerprint of a compound and help mode assignment in the often congested fingerprint region. The cross-peak amplitudes in oMSBA, pMSBA, and OSPA were compared with the theoretical predictions based on the computed values for the off-diagonal anharmonicities and a reasonable match is found. The SO stretching mode provides means for assigning other modes in the fingerprint region and constitutes a promising structural reporter for the 2DIR and RA 2DIR spectroscopy measurements. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of a series of photochromic ruthenium sulfoxide complexes of the form [[Ru[(bpy).sub.2](OSOR)].sup.+] (bpy = 2,2'-bipyridine and OSOR = 2-(benzylsulfinyl)benzoate (OSOBn), 2-(naphthalene-2-yl-methylsulfinyl)-benzoate (OSONap) or 2-(pentafluorophenylmethanesulfinyl)benzoate (OSOBn[F.sub.5])) are described. The excited state distortion is attributed to low frequency metal-ligand and S[double bond]O vibrational modes, which are involved in the isomerization pathway.

Data that support nanosecond and picosecond S-O isomerization of bound dmso in [Ru(tpy)(bpy)(dmso)].sup.2+]] and trans-[Ru(tpy)(pic)(dmso)].sup.+]] are presented. The fast isomerization rates and large isomerization quantum yields are suggestive of electronic structures, which efficiently access the stored potential energy with a metal-to-ligand charge-transfer (MLCT) excited state.

Research has been conducted on cis- and trans-[Ru(bpy) (sub)2 (dmso) (sub)2] (super)2+. The authors describe phototriggered Ry-D (approaches) Ru-O and thermal Ru-O (approaches) Ru-S intramolecular linkage isomerization in this complex.

We investigate a class of non-emissive conjugated polymers with very short excited state lifetimes believed to undergo singlet fission and relaxation to mid-gap forbidden excited states. Poly(3-decylthieneylenvinylene) (P3DTV) and its heavy atom analog, poly(3-decylseleneylenvinylene) (P3DSV), are strongly aggregating conjugated polymers that experience large excited state displacements along multiple vibrational modes. We demonstrate this Franck–Condon vibrational activity effectively disperses excitation energy into multiple non-radiative channels that can be explained using a simple, two-state potential energy surface model. Resonance Raman spectroscopy is sensitive to early Franck–Condon vibrational activity and we observe rich harmonic progressions involving multiple high frequency CC backbone symmetric stretching motions (∼1000–1600 cm−1) in both systems reflecting mode-specific excited state geometrical displacements. Transient absorption spectra confirm that efficient non-radiative processes dominate excited state relaxation dynamics which are confined to π-stacked aggregated chains. Surprisingly, we found little influence of the heteroatom consistent with efficient vibrational energy dissipation. Our results highlight the importance of aggregation and multi-dimensional Franck–Condon vibrational dynamics on the ability to harvest excitons, which are not usually considered in materials design and optimization schemes. [ABSTRACT FROM AUTHOR]

Ultrafast isomerization reactions underpin many processes in (bio)chemical systems and molecular materials. Understanding the coupled evolution of atomic and molecular structure during isomerization is paramount for control and rational design in molecular science. Here we report transient X-ray absorption studies of the photo-induced linkage isomerization of a Ru-based photochromic molecule. X-ray spectra reveal the spin and valence charge of the Ru atom and provide experimental evidence that metal-centered excited states mediate isomerization. Complementary X-ray spectra of the functional ligand S atoms probe the nuclear structural rearrangements, highlighting the formation of two metal-centered states with different metal-ligand bonding. These results address an essential open question regarding the relative roles of transient charge-transfer and metal-centered states in mediating photoisomerization. Global temporal and spectral data analysis combined with time-dependent density functional theory reveals a complex mechanism for photoisomerization with atomic details of the transient molecular and electronic structure not accessible by other means. [ABSTRACT FROM AUTHOR]

Phototriggered linkage isomerization in crystals and films was investigated.

Research is presented concerning the use of spectroscopy to investigate the electrochemistry of a chelating nucleoside which enables the creation of a series of metallonucleosides. The incorporation of metal complexes into DNA is discussed.

Research was conducted to examine the spectroscopy and electrochemistry of mer-(RuCl3(dmso)(tmen)). The mer-(RuCl3(dmso)(tmen)) structure features an S-bonded dmso ligand trans to one N-atom donor from tmen. The Ru-S and S-O bond lengths of S-bonded (Ru(NH3)5(dmso))2+ are much shorter and longer, respectively than those of mer-(RuCl3(dmso)(tmen)). Results indicate that S(dmso) sigma-donation to Ru is extensive in the Ru(III) and Ru(IV) states.

The synthesis and characterization of homoleptic copper carbonyl cations Cu(CO) (super +), Cu(CO)2 (super +) and Cu(CO)3 (super +), are presented. The synthesis involves the exposure of crystalline CuAsF6 to solid CO as less than one atmosphere CO. IR and Raman spectroscopic analyses showed two-coordinate, linear structure for the Cu(CO)2 (super +) cation and a three-coordinate, trigonal-planar structure for the Cu(CO)3 (super +) cation.