Search

Metal–organic frameworks (MOFs) have garnered significant interest owing to their tunable structures and versatile properties. In this study, the construction of MOF-74 analogues based on pre-installation of functional ligands has been investigated. Five distinct ligands and their corresponding complexes are synthesized and characterized. The ligands are strategically designed to impart specific functional groups, enabling enhanced reactivity and tailored properties. Building upon the previously synthesized compounds, an efficient method for the directional functionalization of MOF-74 analogues under moderate conditions has been outlined. This method involves pre-installation through directive substitution of the ligands with suitable functional groups viz. –F, –Br, –I, –CH3 and –CN, allowing precise control over the resulting MOF's properties and functionalities. The study presents the characteristics and properties of [Cu(L1)]n (1), [Cu(L3)]n (2), [Cu(L4)]n (3), [Cu(L5)]n (4) and [Cu(L6)]n (5) complexes, highlighting their distinct features and potential applications. The findings from this research contribute to the fundamental understanding of MOF-74 analogues' synthesis and the efficient functionalization of these materials. The outlined methodology opens new avenues for the tailored design of MOFs with desired properties, enabling their potential utilization in diverse applications, such as catalysis, gas storage and luminescence sensing properties. [ABSTRACT FROM AUTHOR]

In the frame of our research aiming to develop efficient triplet-emitting materials, we are exploring the concept of introducing additional heavy atoms into cyclometalated transition metal complexes to enhance intersystem-crossing (ISC) and thus triplet emission through increased spin–orbit coupling (SOC). In an in-depth proof-of-principle study we investigated the double cyclometalated Pt(II) complexes [Pt(C^N^C)(PnPh3)] (HC^N^CH = 2,6-diphenyl-pyridine (H2dpp) or dibenzoacridine (H2dba); Pn = pnictogen atoms P, As, Sb, or Bi) through a combined experimental and theoretical approach. The derivatives containing Pn = P, As, and Sb were synthesised and characterised comprehensively using single crystal X-ray diffraction (scXRD), UV-vis absorption and emission spectroscopy, transient absorption (TA) spectroscopy and cyclic voltammetry (CV). Across the series P < As < Sb, a red-shift is observed concerning absorption and emission maxima as well as optical and electrochemical HOMO–LUMO gaps. Increased photoluminescence quantum yields ΦL and radiative rates kr from mixed metal-to-ligand charge transfer (MLCT)/ligand centred (LC) triplet states are observed for the heavier homologues. Transient absorption spectroscopy showed processes in the ps range that were assigned to the population of the T1 state by ISC. The heavy PnPh3 ancillary ligands are found to enhance the emission efficiency due to both higher Pt–Pn bond strength and stronger SOC related to increased MLCT character of the excited states. The experimental findings are mirrored in hybrid (TD-)DFT calculations. This allowed for extrapolation to the rather elusive Bi derivatives, which were synthetically not accessible. This shortcoming is attributed to the transmetalation of phenyl groups from BiPh3 to Pt, as supported by experimental NMR/MS as well as DFT studies. [ABSTRACT FROM AUTHOR]

Starting from imidazolium chlorides bearing bulky nitrogen donors, a series of four complexes, mainly [Cu (C^N)Cl]n coordination polymers were obtained directly as luminescent species by simple filtration from the aqueous reaction medium, highlighting a simple, eco-friendly, robust and reproducible synthetic procedure. Additionally, we have shown on the most efficient example that chloride could be exchanged very easily by other halides/pseudohalides (Br-, I-, NCS-, N3 -) allowing to slightly modulate the emitted colour while conserving the polymeric structure, except for azide for which a dimer was obtained. The combination of chemical analyses, of photoluminescence studies in the solid state including quantum yield measurement and X-ray diffraction on single crystals and as-synthesized microcrystalline powders highlighted that the polymeric luminescent species was indeed obtained directly by simple filtration and that no major alteration of the structure was observed upon recrystallisation. Samples of all polymeric complexes displayed remarkable stability towards air oxidation remaining unchanged upon storage for several months and partially retaining their photoluminescence properties even after a thermal treatment at 100 °C for 24 h. [ABSTRACT FROM AUTHOR]

Based on a cationic layered Zn-MOF (1⊃NO3−) with free NO3− anions located in the interlayer channels, two anion-exchanged compounds (1⊃ClO4− and 1⊃BF4−) were achieved by replacing free NO3− anions with ClO4− or BF4− anions. However, an anion-induced structural transformation occurred during the Cl− anion exchange with coordinated NO3− anions replaced by Cl−anions, resulting in the formation of a 2D hcb layered structure (2) and a 3D ths framework (3). The transformation process is fully investigated by means of FT-IR, PXRD and SC-XRD, revealing anion-dependent structural dynamism of the framework. More interestingly, these MOFs demonstrated anion-dependent tunable luminescence evidenced by different fluorescence intensities in the solid state as well as highly sensitive but varied detection capabilities for nitroaromatics. Thus, the MOFs presented here can be used as an ideal platform to deeply explore the possible transformation mechanism, and various tunable luminescent behavior related to the nature of anions, including sizes/shapes, geometries, their coordinating tendencies to metal, and their different hydrogen-bonding abilities with the framework. [ABSTRACT FROM AUTHOR]

The rational design of ESIPT-capable metal complexes (ESIPT – Excited State Intramolecular Proton Transfer) requires two sites, namely, an ESIPT site and a metal binding site, to be spatially separated into the ligand core. Ligands featuring such sites are able to bind metal ions without being deprotonated upon their coordination. The use of ESIPT-capable ligands for the synthesis of metal complexes paves the way toward the exploration of ESIPT in the field of coordination chemistry. In this study, we present a new ESIPT-capable ligand on the base of 1-hydroxy-1H-imidazole, 1-hydroxy-5-methyl-4-[(2,2′-bipyridin)-6-yl]-2-(pyridin-2-yl)-1H-imidazole (HLb), and a series of ESIPT-capable zinc(II) halido complexes, [Zn(HLb)X2] (X = Cl, Br, I). Due to the incorporation of a (2,2′-bipyridin)-6-yl group at position 4 of the imidazole cycle, HLb acts as an N,N,N-chelating ligand. In the solid state, HLb and [Zn(HLb)X2] emit in the yellow region of the spectrum with excited state lifetimes in the nanosecond domain. Chelation-induced emission enhancement (CHEF) effect in zinc(II) complexes leads to an increase in the photoluminescence quantum yield (PLQY) for these compounds in comparison with free HLb ligand. The ESIPT process in HLb and [Zn(HLb)X2] is barrierless. The emission of [Zn(HLb)X2] is associated with the S1T → S0 transition in the tautomeric form (T-form). In contrast, due to (i) the dark nature of the S1 state and the bright nature of the S2 state and (ii) the large S1–S2 energy gap, HLb shows weak S2T → S0 fluorescence, in violation of Kasha's rule. Finally, the analysis of atomic charges in a series of ESIPT-capable 1-hydroxy-1H-imidazoles and their zinc(II) complexes allowed us to reveal the influence of expanding π-conjugation in the proton-donating and proton-accepting moieties on the stabilization/destabilization of the T-form and on the position of the emission band. [ABSTRACT FROM AUTHOR]

Four Zn(II) metal–organic coordination polymers (Zn-MCPs), [Zn2(O-cpia)(2,2′-bpy)·OH] (1), Zn2(O-cpia)(4,4′-bpy)0.5·OH (2), Zn3(O-cpia)2(bpp)2·H2O (3) and [Zn4(O-cpia)2(phen)2·(OH)2] (4), were synthesized by using the mixed ligand approach, namely 5-(2-carboxyl-phenoxy)-1,3-benzenedicarboxylic acid (O-cpiaH3) and different auxiliary N-donor ligands 2,2′-bipyridine (2,2′-bpy), 4,4′-bipyridine (4,4′-bpy), 1,3-di(4-pyridyl)propane (bpp), and 1,10-phenanthroline (phen). The four Zn-MCPs exhibited different architectures based on different secondary building units (SBUs) and different ligand bridging modes. Four adjacent Zn2+ ions and two μ3-OH groups formed [Zn4(μ3-OH)2] tetranuclear SBUs in 1, 2, and 4, further linking together to build different frameworks by different ligand bridging modes. Moreover, the [Zn4(μ3-OH)2] units are composed of Zn(II) ions in different coordination environments. 3D (1) is composed of [Zn4(μ3-OH)2] containing [Zn1O5] and [Zn2O4N2] units by an O-cpia linker. 3D (2) consists of [Zn4(μ3-OH)2] with [Zn1O4N1] and [Zn2O4] units via O-cpia/4,4′-bpy mixed ligands. 3D (3) comes from [Zn2(COO)4] ([Zn2O4N1]) and [Zn1O2N2] by O-cpia/bpp mixed ligands. 2D network (4) is composed of [Zn4(μ3-OH)2] with [Zn1O4N2], [Zn2O5], [Zn3O5], and [Zn4O4N2] units by O-cpia ligands. Luminescence sensing studies revealed that 1 detected 2,2-bis(4,4′-hydroxyphenyl)-propane (BPA) and imipramine hydrochloride (IMH) with detection limits of 1.495 × 10−6 M and 9.92 × 10−5 M, respectively. The sensing mechanism is attributed to the absorption of BPA/IMH under excitation. [ABSTRACT FROM AUTHOR]

Solvothermal reactions between three bis-pyridine-bis-amide ligands containing a fluorene scaffold bearing different substituents on the C9 position (CH2, 1; CMe2, 2; C＝O, 3) with 2,6-naphthalenedicarboxylic acid (H2ndca) and Zn(NO3)2·6H2O led to the isolation of three new microporous mixed-ligand MOFs (PUM310, containing 1; PUM310Me2, containing 2; PUM310CO, containing 3). The structural characterization conducted with X-ray quality single crystals revealed parallel polycatenated frameworks of thick layers in all cases, corresponding to the topological type 5,6L18. The entangled nets contain complete and truncated Zn-paddle wheels. In the truncated paddle wheel, a pyridine of the bis-amide linker has been replaced by a DMF molecule. Solvent removal leads to framework rearrangement, as evidenced by XRPD analysis performed on desolvated PUM310, with consequent framework shrinkage as also evidenced by volumetric adsorption analyses. The three MOFs are fluorescent in the solid state. The optical spectra are indicative of a Förster resonance energy transfer (FRET) involving ndca2− as an excitation energy donor and the bis-pyridine linkers as acceptors, with a FRET efficiency close to 100% in the case of PUM310CO. [ABSTRACT FROM AUTHOR]

As a luminescent material with excellent structural diversity and optical tunability, cuprous iodide organic–inorganic hybrid semiconductors have attracted extensive attention in the field of environmental friendly solid-state lighting (SSL). In order to systematically study how tiny changes in ligands influence the luminescence properties of their complexes, in this study, the tail atoms of ethyl groups in ligands are modified with halogen atoms (F, Cl, and Br) and four all-in-one (AIO)-structured cuprous iodide inorganic–organic hybrid semiconductor materials (Cu2I4(Ln)2) are successfully obtained. The adjustment of the tail atoms effectively regulated the stacking modes of Cu2I42− clusters and their luminescence properties, realizing the transition of the crystal luminescence color from blue to green with the internal quantum yield (IQY) increasing from 1.57% to 53.39%. Their optical diffuse reflectance spectra and density functional theory calculations (DFT) helped investigate the origin and mechanism of luminescence. They are very stable and have good solution processability, which means that they can be applied as rare-earth element-free lighting phosphors. This study can provide ideas and a theoretical basis for designing cuprous iodide cluster luminescent materials in future. [ABSTRACT FROM AUTHOR]

The reaction of Ln(NO3)2·6H2O (Ln = Eu, Tb, Dy and Sm) with (R)-(−)-α-methoxyphenylacetic acid (R-HMPA) and 1,10-phenanthroline (phen) in EtOH/H2O allows the isolation of 1D chiral compounds of formula [Ln(μ-R-MPA)(R-MPA)2(phen)]n in which Ln = Eu (R-Eu), Tb (R-Tb), Dy (R-Dy) and Sm (R-Sm). The same synthesis by using (S)-(+)-α-methoxyphenylacetic acid (S-HMPA) instead of (R)-(−)-α-methoxyphenylacetic acid allows the isolation of the enantiomeric compounds with formula [Ln(μ-S-MPA)(S-MPA)2(phen)]n where Ln = Eu (S-Eu), Tb (S-Tb), Dy (S-Dy) and Sm (S-Sm). Single crystal X-Ray diffraction measurements were performed for compounds R/S-Eu , R/S-Tb , S-Dy and S-Sm. The luminescence and the circular dichroism measured in the solid state are reported. All compounds show sensitized luminescence, notably the Eu3+ and Tb3+ ones, whose emission color can be perceived by the naked eye. For the Eu3+ and Tb3+ derivatives the quantum yield and the circular polarized luminescence have been measured. For the magnetic allowed transition 5D0 → 7F1 of the Eu3+ compound, the anisotropy factor glum is ±0.013 (+for S-Eu). Also, magnetic properties of all compounds were studied with the Dy3+ analogue showing slow relaxation of the magnetization under a direct current magnetic field of 1000 Oe. [ABSTRACT FROM AUTHOR]

A pair of chiral metal–organic frameworks based on enantiomers of chiral Zn(salen) ligands has been successfully obtained by solvothermal subcomponent self-assembly. Both chiral MOFs were characterized by infrared spectroscopy, UV-vis absorption spectroscopy, thermogravimetric analysis, and single-crystal/powder X-ray diffraction. They crystallize in the chiral space group I222 and possess an extended 2D network with a sql topology. Moreover, these MOFs exhibit circularly polarized luminescence (CPL) with a dissymmetry factor of about 3.7 × 10−3. This work provides a simple strategy to make CPL-active MOF materials based on salen ligands. [ABSTRACT FROM AUTHOR]

Herein, a series of ionic mononuclear Cu(I) complexes, [Cu(phen)(bdppmapy)]Cl (1a), [Cu(phen)(bdppmapy)]Br (2a), [Cu(phen)(bdppmapy)]I (3a), [Cu(phen)(bdppmapy)]SCN (4a), [Cu(Dpq)(bdppmapy)]Cl (1b), [Cu(Dpq)(bdppmapy)]Br (2b), [Cu(Dpq)(bdppmapy)]I (3b) and [Cu(Dpq)(bdppmapy)]SCN (4b) {phen = [1,10]phenanthroline; Dpq = pyrazino[2,3-f][1,10]-phenanthroline; bdppmapy = N,N-bis((diphenylphosphino)methyl)-2-pyridinamine} have been synthesized and characterized by using IR, NMR, elemental analysis, single crystal X-ray diffraction analysis, fluorescence spectroscopy methods, and UV-vis and terahertz (THz) time-domain absorption spectroscopy. Their crystal structures were elucidated by X-ray crystallography and their photophysical properties were investigated in detail. All the above complexes exhibit a 1D to 3D supramolecular structure which is linked together by intermolecular weak interaction forces and hydrogen bonds. By regulating ligands and anions, the emission wavelengths of these complexes are quite different in the range from 533 nm to 604 nm. Theoretical calculations and photophysical properties indicate that luminescence is derived from metal-to-ligand charge transfer (MLCT) excited states. In the meantime, the results of calculations show that the stabilization of the increased conjugation of the ligand-based π* orbital is ascribed to the observed bathochromic-shift in the MLCT transitions. [ABSTRACT FROM AUTHOR]

Two diglycolamide (DGA) derivatives having n-butyl (nBuDGA) and s-butyl (sBuDGA) groups have been used for the extraction of Am3+ and Eu3+ to study the role of alkyl chain branching on their separation behaviour. Interestingly, the selectivity between Am3+ and Eu3+ reversed upon changing the ligand from nBuDGA to sBuDGA. An opposite trend was also observed in the extraction of lanthanide ions along the series of decreasing ionic radii for these two ligands. Luminescence and FTIR studies suggest a different nature of the Eu3+ complexes of these two ligands. DFT studies were performed to find out the structure and the electronic distribution of the Am3+ and Eu3+ complexes of these two ligands. [ABSTRACT FROM AUTHOR]

A series of coordination polymers, namely [Zn(μ3-L)(H2O)2] (1), [Zn(μ2-L)(2,2′-bpy)(H2O)] (2), [Zn(μ3-L)(μ2-4,4′-bpy)0.5] (3), [Cd(μ3-L)(2,2′-bpy)] (4), and [Cd(μ2-L)(phen)(H2O)] (5) (H2L = 3-carboxy-1-(3′-carboxybenzyl)-2-oxidopyridinium, 2,2′-bpy = 2,2′-bipyridine, 4,4′-bpy = 4,4′-bipyridine, phen = 1,10-phenanthroline), have been synthesized under hydrothermal conditions. These coordination polymers have been characterized by single-crystal X-ray diffraction, elemental analyses, infrared spectroscopy, thermogravimetric analyses and powder X-ray diffraction. The structure analysis by single crystal X-ray diffraction reveals that compound 1 shows a 1D double chain which can be expanded to a 2D supramolecular architecture through intermolecular π–π stacking interactions. In compound 2, the 1D wave-like chains are extended to a 3D supramolecular framework by intermolecular hydrogen bonds and π–π stacking interactions. In compound 3, the infinite rod-like metal ion chains are linked with L2− anions and 4,4′-bpy to form a 3D framework. In compound 4, the adjacent 1D loop-like chains are interconnected to a 3D supramolecular framework by intermolecular hydrogen bonds and π–π stacking interactions. Compound 5 displays a 3D supramolecular architecture extended from the 1D zigzag chains by intermolecular hydrogen bonds and π–π stacking interactions. The result reveals that the organic ligand plays a key role in the self-assembly of coordination polymers. The luminescence sensing experiments reveal that compounds 1–5 can effectively detect Fe3+, Cr2O72−, and NB. In particular, compound 1 shows a high quenching constant and a low limit of detection for Fe3+. [ABSTRACT FROM AUTHOR]

The ability of 1-hydroxy-1H-imidazoles to undergo proton transfer processes and to exist in N-hydroxy and N-oxide tautomeric forms can be used in coordination chemistry for the design of ESIPT-capable complexes. A series of ESIPT-capable zinc(II) complexes [Zn(HL)Hal2] (Hal = Cl, Br, I) with a rationally designed ESIPT-ligand 1-hydroxy-5-methyl-2,4-di(pyridin-2-yl)-1H-imidazole (HL) featuring spatially separated metal binding and ESIPT sites have been synthesized and characterized. Crystals of these compounds consist of a mixture of two isomers of [Zn(HL)Hal2]. Only a major isomer has a short intramolecular hydrogen bond O–H⋯N as a pre-requisite for ESIPT. In the solid state, the complexes [Zn(HL)Hal2] demonstrate temperature- and excitation wavelength dependent fluorescence in the cyan region due to the interplay of two intraligand fluorescence channels with excited state lifetimes spanning from 0.2 to 4.3 ns. The coordination of HL by Zn2+ ions results in an increase in the photoluminescence efficiency, and the photoluminescence quantum yields (PLQYs) of the complexes reach 12% at λex = 300 nm and 27% at λex = 400 nm in comparison with the PLQY of free HL of ca. 2%. Quantum chemical calculations indicate that N-hydroxy–N-oxide phototautomerization is both thermodynamically and kinetically favourable in the S1 state for [Zn(HL)Hal2]. The proton transfer induces considerable geometrical reorganizations and therefore results in large Stokes shifts of ca. 230 nm. In contrast, auxiliary ESIPT-incapable complexes [ZnL2][Zn(OAc)2]2·2H2O and [ZnL2][ZnCl2]2·4H2O with the deprotonated ligand exhibit excitation wavelength independent emission in the violet region with the Stokes shift reduced to ca. 130 nm. [ABSTRACT FROM AUTHOR]

A series of heteroleptic Cu(I) complexes of type [Cu(N^N)(POP)]+, with POP: bis-[2-(diphenylphosphino)-phenyl]ether and different phenanthroline-based N^N ligands were investigated using density functional theory (DFT) and time-dependent DFT (TD-DFT). The complexes comprise N^N ligands with different bulky substituents at the 2,9 positions, and the addition of phenyl substituents at the 4,7 positions is also investigated. Furthermore, in the complex with the bulkier N^N ligand, the effect of unsaturated hydrocarbon chains added and the presence of dimethylamine electron donor groups were analyzed. The composition/energies of the frontier orbitals and the emission energies were determined for all complexes. Besides, we evaluated the steric effects induced by different N^N ligands in electronic (Pauli repulsion energy) and structural (root-mean-square deviation) terms to determine their influence on the photoluminescence efficiency comparing the properties of the proposed Cu(I) complexes with four reported complexes. The analyzed data allow us to find simple relationships to predict the radiative (kr) and non-radiative (knr) constants based on the steric effects that each complex undergoes according to the type of N^N ligand used, obtaining the best balance (higher kr and lower knr) in complexes with bulkier substituents. Therefore, these complexes could be proposed as suitable luminescent materials for optical applications. [ABSTRACT FROM AUTHOR]

α-Diimine-Cu(I)--diphosphine complexes are good phosphorescence materials at room temperature; however, so far, most reported systems have been mononuclear and homonuclear Cu(I) complexes, and little attention has been paid to heteronuclear Cu(I) complexes. On the other hand, some of the heteronuclear Cu(I)--Ag(I) complexes have displayed enhanced luminescence properties compared to homonuclear analogues, and this inspires us to explore the synthesis and luminescence behaviour of hetronuclear α-diimine-Cu(I)--Ag(I)--diphosphine complexes. Herein, 2-(6-bromo-2-pyridyl)-1Himidazo[4,5-f][1,10]phenanthroline (bpipH) and its four homobinuclear Cu(I)--Cu(I) complexes (1a, 2a, 1b and 2b) and two heterobinuclear Cu(I)--Ag(I) complexes (1c and 2c) were synthesized. All the Cu(I) and Ag(I) centers show typical distorted tetrahedral configurations. Both homobinuclear complexes (1b and 2b) and heterobinuclear analogues (1c and 2c) of deprotonated bpipH ligands show better luminescence than the corresponding homobinuclear complexes (1a and 2a) of the neutral bpipH. Most importantly, compared with the corresponding homobinuclear complexes, heteronuclear Cu(I)--Ag(I) complexes distinctly show further enhanced luminescence and dual emission bands (501 and 601 nm for complex 1c, and 506 and 603 nm for complex 2c), which probably result from 3(LL + ML + IL)CT transitions. Here, the better emission behaviour of heteronuclear α-diimine-Cu(I)--Ag(I)--diphosphine complexes proves that introducing Ag(I) ions to the α-diimine-Cu(I)--diphosphine systems is worth exploring to enhance the luminescence intensity and tune the luminescence colors. [ABSTRACT FROM AUTHOR]

Dinuclear gold(I) compounds are of great interest due to their aurophilic interactions that influence their photophysical properties. Herein, we showcase that gold–gold interactions can be influenced by tuning the electronic properties of the ligands. Therefore, various para substituted (R) N,N′-bis(2,6-dimethylphenyl)formamidinate ligands (pRXylForm; Xyl = 2,6-dimethylphenyl and Form = formamidinate) were treated with Au(tht)Cl (tht = tetrahydrothiophene) to give via salt metathesis the corresponding gold(I) compounds [pRXylForm2Au2] (R = –OMe, –Me, –Ph, –H, –SMe, and –CO2Me). All complexes showed intense luminescence properties at low temperatures. Alignment with the Hammett parameter σp revealed the trends in the 1H and 13C NMR spectra. These results showed the influence of the donor–acceptor abilities of different substituents on the ligand system which were confirmed with calculated orbital energies. Photophysical investigations showed their lifetimes in the millisecond range indicating phosphorescence processes and revealed a redshift with the decreasing donor ability of the substituents in the solid state. [ABSTRACT FROM AUTHOR]

Three-coordinate mononuclear copper(I) halide complexes (1 (I) and 2 (Br)) that bear a novel rigid diphosphine ligand derived from a benzimidazole skeleton were prepared and characterized. Structural analyses of 1 and 2 reveal that the rigidity of the functionalized diphosphine ligand leads to weak Cu⋯πimidazole interactions. Solid state luminescence studies show that the existence of cation–π interactions and the heavy atom effect facilitate orange-red emission (630 nm for 1 and 615 nm for 2) with high photoluminescence quantum yields (65% and 72% for 1 and 2, respectively) and decay times of a few tenths of microseconds. The combination of experimental results and quantum-chemical calculations reasonably reveals that the emission origin is assigned to TADF-assisted phosphorescence based on (metal + halide) to ligand transitions. This systematic study demonstrates that the introduction of a functional π-conjugated bridging moiety between the two P atoms in the diphosphine ligands is a promising strategy for developing new structures with high luminescence performance. [ABSTRACT FROM AUTHOR]

This study presents a molecular surface modification approach to synthesizing a family of silver chalcogenolate clusters (SCCs) containing the same [Ag12S6] core and different surface-bonded organic ligands (DMAc or pyridines; DMAc = dimethylacetamide), with the aim of tuning the luminescence properties and increasing the structural stability of the SCCs. The SCCs displayed strong and tuneable luminescence emissions at 77 K (from green to orange to red) as influenced by the peripheral pyridine ligands. In addition, SCC 5 protected by pyridine molecules was stable in ambient air, humid air and even liquid water for a long time (up to 1 week), and it was more structurally stable than SCC 1 bonded with DMAc molecules under the same conditions. The high structural stability of SCC 5 can be explained by the ability of pyridine molecules to form strong coordination bonds with silver atoms. This study offers a new way of designing structurally stable metal nanoclusters with tuneable physicochemical properties. [ABSTRACT FROM AUTHOR]

Four Zn(II)-based coordination polymers (CPs), [Zn(4-tkpvb)(FB)2] (CP1), [Zn(4-tkpvb)(CB)2] (CP2), [Zn(4-tkpvb)(BB)2] (CP3) and [Zn(4-tkpvb)(NTP)]n (CP4), were prepared from solvothermal reactions of Zn(NO3)2·6H2O with 1,2,4,5-tetrakis((E)-2-(pyridin-4-yl)vinyl)benzene (4-tkpvb) in the presence of 3-fluorobenzoic acid (HFB), 3-chlorobenzoic acid (HCB), 3-bromobenzoic acid (HBB) and nitroterephthalic acid (H2NTP). These four compounds were structurally characterized by IR, elemental analysis, powder X-ray diffraction and single-crystal X-ray diffraction. CP1–CP3 have similar one-dimensional (1D) zigzag chain structures assembled by 4-tkpvb connecting the [ZnL2] (L = FB, CB, BB) units. CP4 displays an unusual 6-fold interpenetrating three-dimensional (3D) net with a 'dia' topology formed by linking the 2D [Zn(NTP)(4-tkpvb)]n layers via 4-tkpvb ligands. CP1–CP4 all exhibited luminescence emission in the solid state. The representative CP3 exhibited good water stability in the pH range from 3 to 13. It was revealed to be an intriguing luminescent probe for CrO42− anions in H2O by a selective fluorescence quenching method or Fe3+ ions in H2O by selective fluorescence enhancement. The detection limit was 0.679 ppm for CrO42− or 0.429 ppm for Fe3+. The emission quenching process may be ascribed to the overlap between the absorption band of the CrO42− anion and those of the excitation and/or emission bands of CP3, while the emission enhancement mechanism was likely due to the weak interaction between Fe3+ and the uncoordinated pyridyl group in CP3. [ABSTRACT FROM AUTHOR]

The present work investigates the synthesis and characterization of a series of cycloplatinated(II) complexes, bearing the dfppy (2-(2,4-difluorophenyl)pyridine) cyclometalated ligand with the general formula of [Pt(dfppy)(Cl)(L)], where L = dmso, dimethyl sulfoxide (A), PPh2py, diphenyl-2-pyridylphosphine (1a), and PPh3, triphenylphosphine (1b). The phosphine-containing dfppy derivatives are photophysically compared with their previously reported ppy (2-phenylpyridine) counterparts. UV-Vis absorption spectra of these complexes were assigned using TD-DFT (time-dependent density functional theory) calculations. It is observed that the wavelengths (low-energy region) used for excitation are related to the mixed 1ILCT/1MLCT/1XLCT electronic transitions. Theoretical investigations on the frontier molecular orbitals of the T1 states confirmed that these transitions are also kept in the triplet excited states and lead to the emissive states with 3ILCT/3MLCT/3XLCT character. This would be experimentally verified by the appearance of the structured emission bands and the 3ILCT being mainly present in the emissive state. However, the dfppy derivatives show dual emission bands (high energy as a structured emission band and low energy as an unstructured emission band) in the solid state, which are not observed in the ppy analogues. The dfppy complexes exhibit spectral blue shifts and have higher quantum yield values compared with the ppy analogs. In this regard, the complexes with PPh2py show stronger emissions than those containing PPh3. [ABSTRACT FROM AUTHOR]

Expanding the family of lanthanide terpyridine coordination polymers has yielded eighteen new complexes with two different phases, Ln(TPC)2(HCOO)(H2O) (Ln-1) and Ln(TPC)(HCOO)2 (Ln-2) (Ln = Sm–Lu, except Tm). Both structures are composed of lanthanide cations interconnected by 2,2′:6′,2′′-terpyridine-4′-carboxylate ligands to yield one-dimensional chain topologies. However, the incorporation of an additional crystallographically unique decorative TPC ligand into Ln-1 gives rises to a distinct phase. The encapsulation of both metal- and ligand-based phosphors within single coordination polymers leads to dual-emission of the afforded materials. Furthermore, judicious lanthanide doping in heterometallic Ln-1 and Ln-2 allows for fine-tuning the photoluminescent colours over a wide range of gamut. Such a combination showcases the capability to fine-tune the emission colours from deep green, to red, and to blue. In addition, direct white-light emission upon UV excitation can be achieved in the Sm x Gd 1−x -1 system. [ABSTRACT FROM AUTHOR]

A small library of dinuclear gold(I) complexes with the title ligands has been prepared, encompassing neutral, mono- and dicationic complexes. The luminescence properties of the complexes in the solid state have been evaluated, and it turns out that neutral and monocationic complexes not presenting a rigid metallamacrocyclic structure can exhibit rather strong emissions that extend towards the red region of the visible spectrum. The in vitro anticancer activity of the complexes has been also preliminarly evaluated; cytotoxicity seems to correlate with complex lipophilicity, whereas selectivity towards cancer cells can be apparently enhanced upon a judicious choice of the ligands. [ABSTRACT FROM AUTHOR]

Two benzene-centered tripodal diglycolamide ligands (LI and LII) were used for the extraction of Am3+ and Eu3+ from nitric acid solutions into a diluent medium of n-dodecane modified with various amounts of isodecanol. The ligands showed preferential extraction of Eu3+ over Am3+ in most cases. While the extraction of the Am3+ ion was not much affected (with a slight increase) over the entire range of diluent compositions in the case of LI, a gradual decline in the extraction of the Eu3+ ion suggested a reversal in the separation trend with Am3+ being preferentially extracted with a solution of LI in pure isodecanol. On the other hand, a sharp decline was seen for the extraction of both Am3+ and Eu3+ in the entire range of diluents containing various fractions of isodecanol when LII was used. The unusual extraction was attributed to the difference in the complexation behaviour of LI and LII, which was explained on the basis of photoluminescence (PL) spectroscopy as well as XAS studies. The PL studies suggested absence of any inner-sphere water molecules from the lifetime data, while the splitting of emisison peaks and asymmetry ratio values gave an idea about the complex geometry. On the other hand, the XAS studies gave information about the bonding in the coordination complexes. [ABSTRACT FROM AUTHOR]

Five new eight-coordinated Nd(III) mononuclear complexes with the formulae [Nd(ntfa)3(EtOH)2] (1), [Nd(ntfa)3(phen)] (2), [Nd(ntfa)3(bipy)] (3), [Nd(ntfa)3(5,5′-Me2bipy)] (4) and [Nd(ntfa)3(4,4′-Mt2bipy)] (5), where ntfa = 4,4,4-trifluoro-1-(naphthalen-2-yl)butane-1,3-dionate, phen = phenanthroline, bipy = 2,2′-dipyridine, 5,5′-Me2bipy = 5,5′-dimethyl-2,2′-dipyridine, and 4,4′-Mt2bipy = 4,4′-dimethoxy-2,2′-dipyridine, were synthesized and structurally characterized. Magnetic measurements were carried out on complexes 2–5. Dynamic magnetic studies revealed single-molecule magnet (SMM) behavior for complexes 2, 4 and 5 with anisotropy energy barriers and preexponential factors of Ueff = 18 cm−1, τ0 = 2.2 × 10−7 s; Ueff = 31 cm−1, τ0 = 1.0 × 10−9 s and Ueff = 19 cm−1, τ0 = 8.7 × 10−8 s, respectively. The ancillary chelating bipyridyl ligands in complexes 2–5 greatly enhance the solid state luminescence emission in the visible and NIR regions through efficient energy transfer from the ligands to the central Nd3+ ion. This study highlights the bifunctionality of the Nd(III) complexes. [ABSTRACT FROM AUTHOR]

Luminescent β-diketone-based lanthanide complexes have been well explored as chemical sensor materials for biomedicine applications. Herein, three mononuclear Eu3+ complexes based on bis-β-diketone ligands (L1, L2 and L3) that can reduce luminescence quenching caused by water were developed. The ligands feature two β-diketone units covalently bound at the 1,8-position of the derivatized anthracene (modified with tetracyanoethylene, TCNE). X-ray crystallographic analysis reveals that their self-assemblies with Ln3+ ions in a 2 : 1 stoichiometric ratio form mononuclear anion complexes, [EuL2]−, in which two ligands coordinate to the metal center in a mutually orthogonal manner. This kind of arrangement together with the bulge of TCNE from the anthracene plane well protected the complexes from the quenching effects of water molecules in the second coordination. The photophysical measurements showed that the complexes not only had high luminescence quantum yields (QYs, up to 50–67%) but also presented excellent water-quenching resistant capability. [ABSTRACT FROM AUTHOR]

Rhenium tricarbonyl complexes are among the most important classes of coordination compounds in inorganic chemistry. Exploring their luminescent excited states, the lowest singlet (S1) and lowest triplet (T1), is an important topic to understand their interesting photophysical behavior and potential applications in organic light-emitting diodes (OLEDs). In this work, a systematic evaluation of the role of zero-field splitting (ZFS) and the geometric arrangement of different nitrogen-donor ligands, including π-stacking interactions, in five selected rhenium luminescent complexes was performed. The optical properties have been deeply discussed using relativistic quantum mechanics methods and other theoretical approaches. Spin–orbit coupling TDDFT (SOC-TDDFT) calculations showed an excellent prediction of emission properties. The zero-field splitting (ZFS) values were relatively large, verifying the presence of the 3MLCT state in the transition character of T1 and efficient spin–orbit coupling (SOC). The introduction of two nitrogen-donor ligands introduced π-stacking interactions that produced a synergistic effect between the ligands and the metal center, promoting blueshift emissions and higher rate constants for T1–S0 transition mediated by SOC. [ABSTRACT FROM AUTHOR]

Platinum compounds are a vital part of our anti-cancer arsenal, and determining the location and speciation of platinum compounds is crucial. We have synthesised a lanthanide complex bearing a salicylic group (Ln = Gd, Eu) which demonstrates excellent cellular accumulation and minimal cytotoxicity. Derivatisation enabled access to bimetallic lanthanide–platinum(II) and lanthanide–platinum(IV) complexes. Luminescence from the europium–platinum(IV) system was quenched, and reduction to platinum(II) with ascorbic acid resulted in a "switch-on" luminescence enhancement. We used diffusion-based 1H NMR spectroscopic methods to quantify cellular accumulation. The gadolinium–platinum(II) and gadolinium–platinum(IV) complexes demonstrated appreciable cytotoxicity. A longer delay following incubation before cytotoxicity was observed for the gadolinium–platinum(IV) compared to the gadolinium–platinum(II) complex. Functionalisation with octanoate ligands resulted in enhanced cellular accumulation and an even greater latency in cytotoxicity. [ABSTRACT FROM AUTHOR]

We report the synthesis and structures of three luminescent dysprosium(III) complexes based on fluorinated alkoxide ligands of formulas [Dy(L1)2(THF)4][BPh4]·0.5THF (1), [Dy(L2)2(THF)5][BPh4]·2.5THF (2) and [Dy(L3)2(THF)5][BPh4]·2THF (3) (L1 = (CF3)3CO−, L2 = C6F5C6F4O−, L3 = C6F5C(CH3)O−). Despite the different dysprosium ion geometries (octahedral vs. distorted pentagonal bipyramidal), these systems exhibit a single-molecule magnet (SMM) behavior, but with distinct relaxation dynamics. Moreover, a typical dysprosium-based luminescence is observed for the three complexes, which make them bifunctional magneto-luminescent SMMs. Remarkably, complex 3 exhibits a high anisotropy barrier of 1469 cm−1 and a blocking temperature of 22 K, making it one of the most performant alkoxide-based SMMs with the highest blocking temperature for a luminescent SMM. [ABSTRACT FROM AUTHOR]

We report the multi-step synthesis of the tetradentate 2-(naphthalen-2-yl)-5-[N,N-bis(2-pyridylmethyl)aminomethyl]-1,3,4-oxadiazole ligand (LTetra-ODA) along with its corresponding [FeII(LTetra-ODA)(NCBH3)2]·1.5CH3OH (C1) complex, which is the first mononuclear 1,3,4-oxadiazole based Fe(II) spin crossover (SCO) complex, and its zinc analogue [ZnII(LTetra-ODA)(NCBH3)2]·0.5H2O (C2). The spin transition is followed by variable temperature (VT-) X-ray crystallography of [Fe(LTetra-ODA)(NCBH3)2]·1.5CH3OH (C1) at 120 and 220 K. The magnetic susceptibility measurements on the bulk sample recorded from 2 to 300 K show that the complex exhibits a complete abrupt reversible spin transition with a T1/2 of 207 K. The loss of the lattice solvent methanol shifts the T1/2 slightly to around 210 K. The spin transition in solution for [Fe(LTetra-ODA)(NCBH3)2]·1.5CH3OH (C1) was followed using the VT-1H-NMR Evans method in CD3CN, with a T1/2 of 357 K. Solid state VT luminescence studies provide some preliminary evidence of interplay of luminescence and spin transition in the [Fe(LTetra-ODA)(NCBH3)2]·1.5CH3OH (C1) complex. [ABSTRACT FROM AUTHOR]

We describe a family of dicationic heteroleptic complexes of the type [Pt(pbt)2(N^N)]Q2, bearing two cyclometalating 2-phenylbenzothiazole (pbt) groups and a N^N phenanthroline-based ligand [N^N = 1,10-phenanthroline (phen) 4, pyrazino[2,3-f][1,10]-phenanthroline (pyraphen) 5, 5-amine-1,10-phenanthroline (NH2-phen) 6], with two different counteranions (Q = CF3CO2 and PF6). Complexes 4–6-PF6 and 4–6-CF3CO2 were obtained through ligand substitution from cis-[Pt(pbt)2Cl2] 2 and cis-[Pt(pbt)2(OCOF3)2] 3, respectively. The molecular structures of 2, 3 and 4-PF6 and the photophysical and electrochemical properties of all complexes were studied in detail. The precursors 2 and 3 exhibit high-energy emissions from 3IL excited states centered on the cyclometalated pbt, with lower efficiency in 2 in relation to 3 by the presence of closer thermally accessible deactivating 3LMCT excited states in 2. The PtIV complexes 4–5-CF3CO2/PF6 display orange emission in CH2Cl2 solution, solid state (298, 77 K) or PS films, arising from a 3IL(pbt) emissive state. The NH2-phen derivatives 6-CF3CO2/PF6 show dual emission associated to two close different emissive states, 3IL′CT (L′ = NH2-phen) and 3IL(pbt), depending on the medium and the excitation wavelength. DFT and time-dependent TD-DFT calculations support these assignments and allow explain the luminescence of these tris-chelate PtIV complexes. [ABSTRACT FROM AUTHOR]