A series of near-infrared-emitting materials of composition A5(V1-x O4)3Cl:Mn x (A = Ca2+, Sr2+, Ba2+; x = 0.00, 0.01, 0.03, 0.05) were prepared and characterized by X-ray diffraction, solid-state NMR, and room-temperature luminescence measurements. Two candidates (Sr5(V0.97O4)3Cl:Mn0.03 and Ba5(V0.97O4)3Cl:Mn0.03) were selected for detailed evaluation as luminescence thermometers. Three single-parameter luminescence thermometry methods (based on relative intensities, band positions, and band widths) were explored. Through multiparametric thermometry, we show that Sr5(V0.97O4)3Cl:Mn0.03 has remarkable performance parameters at physiological temperature (308 K): temperature relative sensitivity S r = 3.14% K-1 and temperature resolution of 0.042 K. The multiparametric approach gives even better accuracy than the best individual readout (that based on luminescence intensity ratio, LIR), while retaining the exceptionally good temperature determination precision of the best single-parametric method (that based on bandwidth). Three different parameter-free full-spectrum luminescence thermometry methods were also applied, giving temperature readout accuracy values ranging from 0.03 to 0.08 K, while maintaining average resolution values of 0.07-0.08 and 0.07 K across the temperature range studied. These performance parameters - coupled with the remarkable brightness in the second biological window (photoluminescence quantum yield of 47%) and the thermal stability at both long-range and local-structure length-scales demonstrated by variable-temperature X-ray diffraction and solid-state NMR, respectivelymake Sr5(V0.97O4)3Cl:Mn0.03 a very promising candidate for luminescence thermometry at physiological temperatures.

Cells must preserve and rewrite transcriptional memory to maintain identity and adapt to stress, yet the physical mechanisms governing this process remain unclear. Recent work implicates genome geometry in encoding transcriptional memory, with nanoscopic chromatin packing domains (PDs) serving as structural units that stabilize or reprogram transcriptional states. One powerful, yet underexplored regulator of this architecture is the nuclear ionic environment. Divalent cations can stabilize PDs through charge screening and phosphate bridging, suggesting a direct physicochemical mechanism linking ions to genome organization. In this study, we show that manipulating nuclear divalent cations is sufficient to reshape chromatin architecture, transcriptional output, and cellular resilience in living human cancer cells. Selective cation depletion (BAPTA-AM, APDAP-AM) produces smaller, less compact PDs and diminishes H3K9me3-enriched heterochromatic cores, structural anchors of transcriptional memory. In contrast, magnesium enrichment enhances packing density and domain maturation. Live-cell nanoscopy reveals that chromatin packing scaling responds within minutes to ionic perturbation. Transcriptomic profiling demonstrates coordinated gene expression changes and reduced adaptive plasticity, while chelator pretreatment increases chemotherapy sensitivity. Together, these findings identify nuclear ions as rapid, reversible regulators of chromatin packing domains and transcriptional memory, revealing ionic homeostasis as a fundamental mechanism linking genome architecture to cellular adaptation.

A Ru(II) complex supported by trans-amido donors is presented. Ru(t2g)-N(2p) dπ-pπ mixing generates highly covalent frontier MOs and strong absorption of visible/NIR light with π-anti-bonding-to-ligand CT character, covering a much wider range than is typical of Ru(II) chromophores. Low-energy irradiation generates a 33 ns excited-state capable of mediating electron-transfer photochemistry.

In this work we report the second ever example of a fully experimentally confirmed thermally activated delayed fluorescence (TADF) in a dinuclear Ir(iii) complex. The said complex displays a singlet-triplet gap Delta EST = 28 +/- 5 meV, in agreement with the computational prediction of 31.1 meV - a value smaller than the previous TADF Ir(iii) complex. We also demonstrate a proof-of-concept, solution-processed OLED featuring this complex as the luminescent dopant in the emissive layer, achieving external quantum efficiency of up to similar to 10% and maximum luminance of 18 000 cd m-2 - values significantly exceeding those reported earlier for Ir(iii) TADF. These findings are preceded by a detailed consideration of spectral signs of TADF in the already known Ir(iii) complexes. The spectral overlap of photoluminescence (PL) with strong (i.e., spin-allowed) absorption bands is unusual for phosphorescent metal complexes, because the PL originates from the triplet state, which is normally significantly lower in energy than the lowest-lying singlet. In this study, we have scrutinized literature data on iridium(iii) complexes that likewise show significant overlap between absorption and PL, and we conclude that a small singlet-triplet energy gap Delta EST in these complexes results in a TADF contribution to their emission. Such a mechanism has hitherto been overlooked in the large body of iridium(iii) chemistry. We use computations to clarify the nature of the excited states in these complexes, demonstrating that the distinctive S1 and T1 character of states can be identified as well as confirming that Delta EST is small enough for TADF to occur at room temperature.

Ortho-aminophenol-N,N,O-triacetate (APTRA) has been widely adopted for binding and sensing Mg2+, although it binds Ca2+ more strongly. This contribution investigates APTRA derivatives that incorporate an aryl-alkynyl fluorophore, addressing how the binding affinities for Mg2+ and Ca2+ are modulated by a substituent R in the aryl ring of the fluorophore. Six such derivatives have been synthesized via their tris-ethyl esters. They feature X ═ CN, CF3, or OMe, as a mesomerically electron-withdrawing, inductively electron-withdrawing, or electron-donating substituent, respectively, with the alkyne either para or meta to the APTRA nitrogen. Study of the absorption and fluorescence properties of the esters reveals the importance of intramolecular charge transfer (ICT) states for X ═ CN and CF3, but not OMe. The corresponding carboxylate ligands are less emissive in water, and the fluorescence is not strongly modulated by metal ions. However, the absorption spectra change markedly, allowing dissociation constants Kd to be evaluated. The key conclusions are that (i) electron-withdrawing substituents attenuate the affinity for Ca2+ more than Mg2+, leading to a net improvement in selectivity for Mg2+, and (ii) the effect is larger when the APTRA nitrogen (as opposed to phenolic oxygen) is para to-and hence directly conjugated with-the alkyne.

The Zn2+ ion has crucial roles in biology, such that the development of fluorescent probes for real-time monitoring of fluctuations in its concentration remains important. We describe a new class of probe that utilizes ortho-aminothiophenol-N,N,S-triacetate (S-APTRA) as the binding site for the metal ion, recently reported to bind Zn2+ with high selectivity over Ca2+ and Mg2+. The S-APTRA unit has been appended with a rosamine fluorophore by a sequence of formylation, condensation with 3-(dimethylamino)phenol, and oxidation. The resulting conjugate S-APTRA-Rosamine fluoresces only weakly in aqueous solution, but its emission is greatly enhanced by Zn2+, probably due to the suppression of a photoinduced electron transfer (PET) quenching process. The probe binds Zn2+ with a dissociation constant, Kd, of 55.7 ± 1.2 nM, matching well with [Zn2+] in many biological cells, with very high selectivity over Ca2+ and Mg2+, and with attractively low-energy emission in the orange-red region. A proof-of-concept imaging experiment in NIH 3T3 cells reveals that the probe can successfully signal changes in [Zn2+] by confocal fluorescence microscopy. Meanwhile, a tetradentate analogue omitting the S-bonded carboxylate also responds to Zn2+ but the affinity is tempered by a factor of around 103. Sulfoxide derivatives of the two systems show no response.

We present the first integration of a platinahelicene within a nanographene (NG), giving access to near-infrared circularly polarized phosphorescence with dissymmetry factors glum reaching 4 × 10-3. For comparison, a novel NG featuring a borahelicene displayed a blue-green circularly polarized fluorescence with glum = 6 × 10-4.

The development of phosphorescent complexes of second-row transition metals remains a goal of molecular design, driven by the generally lower cost, higher abundance and thus improved sustainability with respect to their applications. In this work, the synthesis, structures, and photophysical characterization of a mononuclear cyclometalallated palladium complex LPdOAc and its acetate-bridged dinuclear analogue [(LPd)2(kappa 2-OAc)]+ are presented, where L represents an NCN-coordinated, cyclometallated 1,3-bis(2-quinolinyl)benzene. The benzannulated ligand stabilizes the dinuclear derivative through ligand-ligand interactions between pi-systems, which is further facilitated by the acetate adopting a kappa 2-binding mode bridging the two Pd(II) centres. The mononuclear (but not the dinuclear) complex is weakly phosphorescent in the deep red region of the spectrum (lambda max = 676 nm) in solution at room temperature, while both compounds phosphoresce in frozen media at 77 K with essentially identical profiles, emission maxima, and lifetimes of 180 mu s. Analysis of the photophysical properties and electronic structures of both monomer and dimer are supported by density functional theory (DFT) and time-dependent DFT (TDDFT) simulations.

Hackmanites are a class of materials that exhibit diverse and intriguing optical characteristics, including luminescence and tenebrescence. Doping with other luminescent species would unveil a fresh spectrum of optical properties and potential applications. This project aimed to successfully dope a lithium derivative of hackmanite with highly luminescent lanthanides (Sm3+, Eu3+, Tb3+, and Dy3+) using a doped aluminosilicate precursor, LiAlSiO4. Initial structural analysis indicated successful doping with little disruption to the host lattice. Luminescence spectroscopy revealed that the emissive properties of the lanthanide ions were largely suppressed upon incorporation into the sodalite due to the presence of other highly luminescent impurities. However, europium-doped samples exhibited emission from both Eu2+ and Eu3+, with the former resulting in long-lasting green persistent luminescence. Room-temperature persistent luminescence was determined to arise from traps at a depth of 0.3 eV. In contrast, doping with samarium yielded a photochromic response atypical of traditional hackmanites, characterized by absorption extending into the near-infrared region. Spectroscopic evidence suggested the involvement of Sm2+/Sm3+ redox processes coupled to disulphide photochromic centers in the tenebrescence mechanism. Lanthanide doping provides a versatile route for modifying both the luminescence and photochromic behavior of hackmanites, enabling additional functionalities in lighting applications and UV dosimetry.

New macrocyclic molecules are described that incorporate Pt(NCN) units on opposite edges of a rectangular structure, with xanthene units constituting the other two sides. Here, NCN represents a cyclometallating tridentate ligand based on 2,6-di(2-pyridyl)benzene or its pyrimidine analog. The complexes display strong photoluminescence peaking in the near-infrared region of the spectrum in solution (λmax up to 761 nm). Photophysical data and DFT calculations indicate that the emission arises from "intramolecular excimers"-triplet excited states that form when the two Pt(NCN) units within the molecule are brought into close proximity to interact interfacially. In doped polymers, the necessary molecular distortion is inhibited, but related excited states that emit in a similar region can still form through intermolecular interactions.

Ortho-aminophenol-N,N,O-triacetate (APTRA) is a pentadentate ligand adopted for the selective binding of Mg2+. It has been incorporated into fluorescent sensors for Mg2+, though it binds Ca2+ and Zn2+ more avidly. Here, the synthesis of a sulfur analogue of APTRA is reported, namely ortho-aminothiophenol-N,N,S-triacetate, referred to as S-APTRA. The binding of this new pentadentate ligand to Zn2+, Ca2+, and Mg2+ has been monitored in buffered aqueous solution by UV absorption spectroscopy. The replacement of the phenolic oxygen of APTRA by a sulfur atom renders S-APTRA capable of binding Zn2+ in a biologically relevant range (Kd = 6.6 ± 0.3 nM) with high selectivity over Mg2+ and Ca2+. The enhanced selectivity for Zn2+ is in line with the principles of "hard and soft acids and bases." A tetradentate analogue omitting the S-appended carboxylate group, S-APDIA, is also reported. Its lower denticity leads to decreased affinity for Zn2+ (Kd = 8 ± 1 μM). The oxidation of S-APTRA and S-APDIA by m-CPBA leads to the sulfoxides SO-APTRA and SO-APDIA, which bind Zn2+ yet more weakly (Kd = 260 ± 20 mM and 3.6 ± 0.3 mM, respectively). This new family of ligands may prove appealing in the development of new carboxylate-based zinc sensors.

The coordination chemistry of the planar, doubly π-extended bipyridine analog, 6,6',7,7'-biphenanthridine (p-biphe), is presented. The phenanthridine units in p-biphe are fused together at the 6- and 7- positions, and the resulting rigid ligand is compared with the more flexible parent "biphe" fused only at the 6-positions. p-Biphe is intensely fluorescent in solution with a much higher quantum yield, but, unlike biphe, at 77 K the fluorescence is not accompanied by any significant phosphorescence. Two four-coordinate Cu(I) complexes and pseudo-octahedral Ru(II) and Ir(III) complexes are described: [Cu(p-biphe)2]+, [(P^P)Cu(p-biphe)]+, [Ru(bpy)2(p-biphe)]2+, and [Ir(ppy)2(p-biphe)]+, isolated as PF6 salts (P^P  =  4,5-bis(diphenylphosphino)-9,9-dimethylxanthene; bpy = 2,2'-bipyridine; ppy = 2-phenylpyridine). The complexes are strongly coloured due to intense low-energy absorption to charge-transfer excited states based on TDDFT calculations. The acceptor nature of the p-biphe ligand is clear from multiple reduction events observed electrochemically. The Ir(III) complex displays remarkably low-energy phosphorescence (λmax = 812 nm) in solution at room temperature with a vibrational progression evident extending into the near IR, with no contamination from visible light emission. While the heteroleptic Cu(I) complex is phosphorescent at 77 K, no emission is detectable from [Cu(p-biphe)2]+ or [Ru(bpy)2(p-biphe)]2+, likely due to competitive nonradiative decay.

Tetradentate proligands based on biphenyl appended at the 3 and 3' positions with pyridin-2-yl rings (H2L1), quinoline-8-yl (H2L3) heterocycles, or one such pyridine and quinoline (H2L2), have been synthesized by palladium-catalyzed cross-coupling. These compounds were expected to undergo cyclometalation with K2PtCl4 to generate Pt(II) complexes, PtL1-3, featuring NCCN-coordinated ligands. For H2L2 and H2L3, the corresponding Pt(IV) compounds PtL2-3Cl2 were initially isolated, from which PtL2-3 could be obtained by reduction with zinc. In contrast, H2L1 gave an unusual Pt(III) dimer, Pt2L12Cl2, and subsequently PtL1 upon reduction. All of the complexes have been structurally characterized in the solid state by X-ray diffraction. The quinoline-containing complexes of L2 and L3 feature one or two 6-membered chelates, respectively, with an accompanying twisting of the quinoline ring(s) relative to the biphenyl unit to allow the metal ion to achieve its preferred square-planar coordination. PtL1 displays intense green phosphorescence in solution at room temperature with a quantum yield of 67%. The deep-red emission of PtL2-3 is weaker due to suppressed triplet radiative rate constants as well as faster nonradiative decay. The Pt(IV) complexes emit only at 77 K, with long lifetimes of around 300 μs, while the Pt(III) dimer shows no detectable emission.

Two new members of the family of NCN -Pt( ii ) complexes have been synthesized. The compounds present new aryl substituents on the pyridine rings and have been deeply characterized, pointing out their high luminescence and QY (89–98%).

4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) and its derivatives are highly useful fluorescent dyes employed in myriad applications in chemistry and biology. Here, we revisit a series of dihalogenated (Cl, Br, I) BODIPY derivatives with rare 1,7-regiochemistry. In addition to their synthesis and structural characterization, we fill in a missing piece of the current literature by delineating their photophysical behavior, including the light-driven generation of singlet oxygen (1O2) which is mediated with particularly high efficiency by the heavier diiodinated congener.

Tetradentate proligands based on biphenyl appended at the 3 and 3' positions with pyridin-2-yl rings (H2L1), quinoline-8-yl (H2L3) heterocycles, or one such pyridine and quinoline (H2L2), have been synthesized by palladium-catalyzed cross-coupling. These compounds were expected to undergo cyclometalation with K2PtCl4 to generate Pt(II) complexes, PtL1-3, featuring NCCN-coordinated ligands. For H2L2 and H2L3, the corresponding Pt(IV) compounds PtL2-3Cl2 were initially isolated, from which PtL2-3 could be obtained by reduction with zinc. In contrast, H2L1 gave an unusual Pt(III) dimer, Pt2L12Cl2, and subsequently PtL1 upon reduction. All of the complexes have been structurally characterized in the solid state by X-ray diffraction. The quinoline-containing complexes of L2 and L3 feature one or two 6-membered chelates, respectively, with an accompanying twisting of the quinoline ring(s) relative to the biphenyl unit to allow the metal ion to achieve its preferred square-planar coordination. PtL1 displays intense green phosphorescence in solution at room temperature with a quantum yield of 67%. The deep-red emission of PtL2-3 is weaker due to suppressed triplet radiative rate constants as well as faster nonradiative decay. The Pt(IV) complexes emit only at 77 K, with long lifetimes of around 300 μs, while the Pt(III) dimer shows no detectable emission.

Luminescent, square-planar platinum(II) complexes often undergo intermolecular interfacial interactions at elevated concentrations, sometimes leading to low-energy emission from excimers or aggregates and thus offering an attractive route to more efficient red-and NIR-emitting phosphors. In this study, we describe two new compounds, (LPt2)-Pt-py and (LPt2)-Pt-iq, in which two Pt(NCNO) units are appended onto a xanthene scaffold to favour the intramolecular formation of such states. The Pt(NCNO) units are based on mononuclear Pt(II) complexes known to be highly emissive, namely those of 5,5-dibutyl-2-(3-(pyridin-2-yl)-phenyl-5H-indeno[1,2-b]pyridine-9-olate in the case of (LPt2)-Pt-py, and its isoquinolin-3-yl analogue for (LPt2)-Pt-iq. X-ray diffraction reveals an anti arrangement of the Pt(NCNO) units relative to one another. The emission spectrum of (LPt2)-Pt-py in solution is dominated by a low-energy band centred at 660 nm, with weaker bands at shorter wavelengths where the corresponding mononuclear complex emits. The former is attributed to excimers that form intramolecularly, but the process is inhibited in a polystyrene host at room temperature, and in a glass at 77 K. Conversely, (LPt2)-Pt-iq displays no such excimer emission in solution, probably due to a less flexible structure impeding the attainment of the necessary geometry at room temperature. In polystyrene films at loadings >25 % by mass, both complexes begin to show low-energy emission from intermolecular excimers or aggregates. In neat films of (LPt2)-Pt-iq, the low-energy band dominates the spectrum, with a remarkably high quantum yield of around 20 %, an order of magnitude higher than (LPt2)-Pt-py.

The non-linear optical and antitumoral properties of cis-Ir(N,C-ppy)2(O,O-THC) have previously been established (where ppy and THC are the deprotonated forms of 2-phenylpyridine and tetrahydrocurcumin, respectively). In the present study, this complex is investigated as a green phosphorescent emitter for an OLED fabricated by solution processing. The device efficiency is similar to that of an analogue employing the archetypal complex cis-Ir(N,C-ppy)2(O,O-acac), but shows a higher luminance at low applied voltages (<6 V). In order to explore whether this effect might be observed in the blue region too, a new derivative has been prepared and characterized, namely cis-Ir(N,C-F2ppy)2(O,O-THC) (F2ppyH = 2-(2,4-difluorophenyl)pyridine). It, too, gives an OLED with a particularly high luminance at low voltage, suggesting a beneficial effect of substituting acetylacetonate by tetrahydrocurcuminate.

Ligands containing phenanthridine (benzo[c]quinoline) have presented notable exceptions to the conventional logic that increasing ligand benzannulation leads to bathochromic (red) shifts in the absorption and emission of their coordination complexes. The counterintuitive blue shifts have been attributed to the peculiar structure of phenanthridines, whose ground states are dominated by imine-bridged biphenyl resonance contributors. These serve to isolate the C=N unit electronically from the rest of the ligand framework and allow the C=N moiety to act as a 'shock-absorber', buffering against larger molecular distortions in a molecule's excited state, and reducing the observed pseudo-Stokes' shift. Here, we provide experimental evidence for this assertion in the form of a counterfactual that reverses this trend: substitution at the phenanthridine 6-position (i. e., at the C=N sub-unit) breaks the phenanthridine's tendency to cause hypsochromic luminescence shifts. The synthesis, full characterization, and comparison of 2-quinolinyl and 6-phenanthridinyl exemplars is provided, supported by a detailed theoretical treatment.

Dinuclear platinum(II) complexes of a new, ditopic, bis-tridentate NCN–NCN-coordinating ligand, appended with four mesityl groups, are reported. The high radiative rate constants and correspondingly efficient luminescence of the complexes involves thermally activated delayed fluorescence (TADF), thanks to a near-zero energy gap between the S1 and T1 states. The mesityl groups also serve to hinder the aggregation that was detrimental to electroluminescence efficiency in previous studies, allowing a ~4 fold increase in OLED efficiency to be achieved (i.e. from 2.3% previously to 10% in this work). Oxidation of one of the Pt(II) complexes led to a dinuclear Pt(IV) complex of unprecedented structure.