Cocrystallization is a versatile supramolecular synthetic strategy for tuning the properties of organic semiconductors (OSCs) and related polycyclic aromatic hydrocarbons (PAHs) by controlling their packing and architectures with suitable coformers. In this study, we demonstrate a supramolecular synthon substitution approach to afford cocrystals of 9,10-diphenylanthracene (DPA) and its isostere 9,10-dipyridylanthracene (DPyA) with halogenated coformers 1,2-diiodotetrafluorobenzene (1,2-C 6 I 2 F 4), 1,4-diiodotetrafluorobenzene (1,4-C 6 I 2 F 4), and 1,3,5-triiodotrifluorobenzene (1,3,5-C 6 I 3 F 3). The strategy enables reliable replacement of [C-I···π] interactions in DPA cocrystals with [C-I···N] interactions in the corresponding DPyA cocrystals. Although coformers and substitutions alter the supramolecular architectures, the photophysical properties and molecular conformations of the OSC building blocks remain largely preserved. The results highlight synthon substitution as a reliable supramolecular design element that accelerates the derivatization of established OSCs and their isosteres, offering opportunities for property modulation.

Main-group-bridged [1]ferrocenophanes enable the incorporation of a variety of elements into polyferrocene materials through ring-opening polymerization. While antimony-containing materials have been used as flame retardants and photolithographic resists, there exists only a single example of a Sb(III) main-chain polymer. We have used the ring-opening of a stiba[1]ferrocenophane as a facile route to expand the family of Sb(III) main-chain polymers. Two examples of stiba[1]ferrocenophanes were synthesized and characterized, featuring bulky mesityl and terphenyl substituents at antimony, fc(SbMes) and fc(SbTer). fc(SbTer) was found to undergo thermal ring-opening polymerization to form a soluble and robust polymeric material, PFSbTer. These results further expand the range of polyferrocenes and provide access to a new class of Sb(III)-containing materials.

As an alternative to macrocyclic chelators, a family of high-denticity, acyclic chelating agents based on picolinate arms has been devised with the aim of finding versatile chelating agents for 225Ac, 161Tb, and 177Lu. This family comprises six symmetrical four-arm decadentate chelators that differ in the nature of the backbone spacer, ethylene (H4 tpaen), o-phenylene (H4 tpaopd), 2,3-naphtylene (H4 tpaond), m-xylylene (H4 tpamxd), p-xylylene (H4 tpapxd), and 2-hydroxypropylene (H4 tpadapo), and two dissymmetrical octadentate ligands, H3 tripaen and H4 asyoctapa, structurally derived from H4 tpaen by the loss of one arm (the first) and the replacement of two vicinal picolinate pendent arms by acetate groups (the second). The coordination chemistry of each chelating ligand with nonradioactive Lu3+, Tb3+, and La3+ (the latter as a surrogate for [225Ac]Ac3+) has been explored to rationalize the findings in radiolabeling and human serum stability studies. With an RCY of 96% at 10-7 M, which is directly comparable to the gold standard macrocyclic chelators H2 macropa and H4 crown, H4 tpaond is an excellent candidate for the development of radiopharmaceuticals based on 225Ac. In addition, both H4 tpaen and H4 tpaopd are also an opportunity for the 225Ac/155Tb theranostic pair. Meanwhile, H4 asyoctapa appears to be a great opportunity, not only for developing terbium radiopharmaceuticals, but also for the promising 177Lu/155Tb pair.

The correlation between increased ligand field strength and longer decay lifetimes in iron(ii) complexes is well established. In this work, we observe an unusual inverse relationship between lifetime and ligand field strength, where a stronger ligand field leads to a shorter lifetime. Two phenanthroline-iron(ii) complexes containing imidazol-2-ylidene (FephenImi) and benzimidazol-2-ylidene (FephenBzi) ligands are reported. Transient absorption experiments in acetonitrile reveal longer 3MLCT and 3MC lifetimes for FephenImi of 9 and 195 ps, respectively, compared to 2 and 53 ps, respectively, for FephenBzi. The 3MLCT lifetime is extended in dichloromethane for FephenImi to 27 ps. The differences in the excited-state dynamics are rationalized using DFT surface analysis. A closer-to-perfect octahedral geometry of FephenImi in the excited state increases the energy of the 3MC state and leads to a kinetic barrier between the triplet states. In contrast, the smaller axial angles in FephenBzi facilitate the 3MLCT → 3MC deactivation pathway despite the higher ligand field strength. These results provide a new perspective on geometric distortions in the excited states that may have an impact on the conversion between triplet states and increase the decay lifetime in iron(ii) complexes.

Orbiculamide A, a macrocyclic peptide with antimitotic and antileukemic properties, contains several synthetically challenging structural motifs, including a 2-bromo-5-hydroxytryptophan residue, that presents a widely recognized synthetic challenge. Here, we report the first total synthesis of orbiculamide A, where central to our approach is a chemoselective, late-stage bromodesilylation strategy. This work provides a foundation for the synthesis of related natural products and scaffold diversification of medicinal peptides.

Platinum(II) complexes have been thoroughly researched for applications in bioimaging and optoelectronics, often searching for potential uses after observing a complex's unique properties. Here, we investigate the role of the bridging atom on the resulting photophysical properties, comparing two tetradentate complexes bearing O and N elemental bridges between 2-phenylpyridine (phpy) units to the well-known unbridged Pt(phpy)2. Unlike the O-bridged complex, single-crystal X-ray diffraction demonstrated no Pt···Pt interactions for the N-bridged complex in the solid state. As anticipated, the introduction of a bridging atom turns on room-temperature phosphorescence. Absorption and emission spectroscopy combined with density functional theory (DFT) calculations explained that the blue-shifted spectra of the O-bridged complex are a result of HOMO stabilization by the more electronegative bridging atom. The minor differences were found to result in macroscopic differences in the properties of the bridged complexes in the solid state and when aggregated. Notably, the N-bridged complex experienced significant aggregation-caused quenching, whereas the O-bridged complex displayed red-to-green aggregation-induced emission switching resulting from excimer emission. In this work, we investigate the photophysical properties of the core structures for a popular family of Pt complexes in hopes of streamlining the rational design of new functional molecules.

Organic multiresonance thermally activated delayed fluorescence (MR-TADF) emitters offer a promising platform for achieving narrowband emission with high color purity, however, tuning emission color into the red region while maintaining high efficiency remains a key challenge. Herein, we report a series of indolo-fused quinolino[3,2,1-de]acridine-5,9-dione (QAO)-based MR-TADF emitters mN-QAO, mN-SQAO, pN-QAO, and pN-SQAO to systematically investigate the impact of fusion position and sulfur locking on their photophysical properties. Positional variation of the indole unit enables efficient color tuning from blue (lambda max = 455 nm) to green emission (lambda max = 516 nm), while preserving narrowband emission (FWHM = 21-24 nm). Incorporation of a sulfur lock further modulates the electronic structure, promoting enhanced charge-transfer (CT) and red-shifted emission with moderate photoluminescence quantum yields (similar to 48%). Combined experimental and theoretical analyses reveal that sulfur locking enhances HOMO delocalization and introduces a balance between short- and long-range CT, which governs the observed emission behavior. Furthermore, the red-emitting pN-SQAO was employed to fabricate water-dispersible glassy organic dots (g-Odots), which retain MR-TADF characteristics in aqueous media and exhibit efficient cellular uptake. Notably, these nanostructures demonstrate lysosomal localization, while further functionalization with a triphenylphosphonium moiety (Mito-pN-SQAO) enables selective mitochondrial targeting. This represents the first example of g-Odots achieving targeted mitochondrial localization. This study establishes a versatile molecular design strategy for tuning MR-TADF properties and expands their applications into targeted bioimaging.

Platinum(II) complexes have been thoroughly researched for applications in bioimaging and optoelectronics, often searching for potential uses after observing a complex's unique properties. Here, we investigate the role of the bridging atom on the resulting photophysical properties, comparing two tetradentate complexes bearing O and N elemental bridges between 2-phenylpyridine (phpy) units to the well-known unbridged Pt(phpy)2. Unlike the O-bridged complex, single-crystal X-ray diffraction demonstrated no Pt & centerdot;& centerdot;& centerdot;Pt interactions for the N-bridged complex in the solid state. As anticipated, the introduction of a bridging atom turns on room-temperature phosphorescence. Absorption and emission spectroscopy combined with density functional theory (DFT) calculations explained that the blue-shifted spectra of the O-bridged complex are a result of HOMO stabilization by the more electronegative bridging atom. The minor differences were found to result in macroscopic differences in the properties of the bridged complexes in the solid state and when aggregated. Notably, the N-bridged complex experienced significant aggregation-caused quenching, whereas the O-bridged complex displayed red-to-green aggregation-induced emission switching resulting from excimer emission. In this work, we investigate the photophysical properties of the core structures for a popular family of Pt complexes in hopes of streamlining the rational design of new functional molecules.

Extracts of the prairie crocus Pulsatilla nuttalliana contain the racemate of the antimitotic dimeric butenolide anemonin (1), that was first discovered over 200 years ago. An in-depth examination of anemonin has resulted in the first resolution and configurational assignment of the trans-anemonin enantiomers and shown that they spontaneously racemize. A persistent minor impurity in the 1H NMR spectra of trans-anemonin samples recorded in several NMR solvents has been identified as the new natural product cis-anemonin (3), and it has been shown that the cis- and trans-anemonin stereoisomers are in equilibrium with each other and with their biosynthetic precursor protoanemonin (2). X-ray diffraction analysis structures have been obtained for (R,R)-trans-anemonin (1b) and cis-anemonin (3). The P. nuttalliana extract also contains the known compound siderin (5) and the new analog chlorosiderin (6).

The ultrafast decay inherent to metal complexes with a 3d6 configuration limits their application as photosensitizers. Despite recent advances in improving the photophysical properties of these complexes, existing ligand designs restrict further modification and are often synthetically challenging. Here, we show how sulfur-bridged ligands can be used to tune the structural and photophysical properties in Co(iii) photosensitizers. Two complexes, CoS ([Co(PTZIm2)2]PF6) and CoSO2 ([Co(PTZO2Im2)2]PF6), adopt facial geometries due to a less rigid ligand backbone compared to other pincer-type ligands. The lowest-lying absorption bands of both CoS and CoSO2 display metal/ligand-to-ligand charge-transfer (M + L)LCT character with different contributions from the sulfur-bridged ligand. TD-DFT analysis indicates that CoSO2 has a lower contribution from the phenothiazine moiety to the band at 400 nm. The sulfur oxidation state also affects the electronic density at the metal center, with CoS showing a lower MIV/III oxidation potential. Transient absorption experiments reveal that fast non-radiative decay channels are facilitated in CoS. However, a photoactive long-lived component (8.0 ns) is also observed. Oxidation of phenothiazine extends the lifetimes of short-lived components in CoSO2, where both electronic and structural effects may be playing a role. These findings demonstrate that the photophysical properties of Co(iii) complexes can be modulated by variation of the sulfur oxidation state to achieve different photophysical properties of the complexes.

The North American fungus Echinodontium tinctorium has not been explored for its small-molecule constituents for 60 years. Herein, we describe chemical investigation of its organic extracts and bioactivity-guided fractionation, which led to the isolation of two new diterpenoids, echinodin A (1) and B (2). Both 1 and 2 contain an unprecedented tetracyclic 5/3/7/5 carbon ring system with the highly constrained cyclopropane motif. Bis-(2,4-dihydroxy-6-methylphenyl) methane (4) was isolated for the first time in a natural source together with four other known compounds (3, 5-7). The structures of 1-7 were determined by a combination of NMR, ESI-MS, and single-crystal X-ray diffraction analyses. Cytotoxic assays revealed that 1, 2, and 4 have weak cytotoxic activity against human cervical adenocarcinoma (HeLa) and human glioblastoma (U251). Echinodol (5) and echinodone (6), investigated for the first time for their bioactivity, exhibited strong cytotoxic activity with IC50 values ranging from 1.2 to 5.5 μM against a panel of human cancer cell lines. A mechanism of action investigation showed that echinodol (5) induced apoptosis and arrested the cell cycle at the S phase in U251 cells. These findings not only highlight the new chemistry and biology of isolated compounds but also position E. tinctorium as a source for further pharmacognostic exploration.

H3tripa (H3macrotripa), a triaza-18-crown-6 macrocycle bearing three picolinate arms, enables quantitative radiolabeling of [203Pb]Pb2+ and [213Bi]Bi3+ and exhibits robust human serum stability. NMR spectroscopy, X-ray crystallography, density functional theory, and UV-potentiometry investigate its coordination geometry and thermodynamics with Bi3+ and Pb2+, highlighting H3tripa as a promising Pb/Bi theranostic chelator.

Herein we report the acid-mediated insertion of isocyanates and isocyanides into the cyclotriphosphane (PtBu)3 to yield 1-imino-2-oxo-3,4,5-triphospholanes (1R) and 1-imino-2,3,4-triphosphetanes (2R), respectively. The insertion of both substrates into (PtBu)3 proceeds in a manner distinct from related insertions into organic substrates such as epoxides and donor-acceptor cyclopropanes. Critically, the insertion of isocyanides proceeds with 100% atom economy, and may be performed using catalytic Brønsted or Lewis acid with only a mild decrease in selectivity. The use of compounds of the type 1R and 2R in coordination chemistry was explored by reaction with [Rh(COD)Cl]2. In both cases the heterocycles bind rhodium selectively through the least sterically encumbered phosphorus atom.

Multiple resonance thermally activated delayed fluorescence (MR-TADF) emitters exhibit short-range charge transfer (SRCT) and have narrow emission, whereas donor-acceptor TADF emitters show long-range charge transfer (LRCT) and rapid reverse intersystem crossing (RISC). While some work has been done to create intermediate-type materials with narrow emission and rapid RISC simultaneously, no studies of structurally comparable donor-acceptor versus MR-TADF systems have been described. Here we report two TADF emitters, Acr-DiKTa and Iso-DiDiKTa, to examine the effect of ring fusion on LRCT and SRCT character. Acr-DiKTa appends an acridone moiety to quinolino[3,2,1-de]acridine-5,9-dione to create a donor-acceptor-type structure, while a carbonyl bridge fuses these moieties in Iso-DiDiKTa to give an MR-TADF structure. Acr-DiKTa emits blue-green in toluene with a full width at half maximum (FWHM) of 38 nm whereas Iso-DiDiKTa emits green-yellow with a FWHM of 34 nm. Calculated orbital distributions show SRCT in the first excited state for both compounds. Both compounds are TADF active in doped films, and derived rate constants show that RISC is four times more rapid in Acr-DiKTa. This study shows that while ring fusion enhances color purity, donor-acceptor structures can achieve comparable FWHMs and rapid RISC through dominant SRCT supported by LRCT for best performance in TADF materials.

One and two site reduction of hexachlorophosphazene using cyclic (alkyl)(amino)carbene substituents are demonstrated. This method is extended to the reduction of poly-chlorophosphazene, yielding a novel inorganic polymer with available lone pairs.

Diarylethenes (DAE) are a well-known class of photochromic compounds with diverse applications ranging from optoelectronic devices to biological sensors. DAEs exhibiting emission in the closed form show potential for super-resolution imaging, however, these are rare because DAEs in the closed form are notorious fluorescence quenchers. Here a series of DAE compounds containing phosphine oxide groups is reported that exhibit turn-on emission and are the first examples of DAEs showing both aggregation-induced emission (AIE) and anti-Kasha emission in the closed form. The molecular design of the DAEs originates from careful selection of diphenylphosphine oxide groups, which have the appropriate bulkiness and electron-withdrawing ability. Furthermore, the emission wavelength can be tuned by substituents, leading to a new class of diarylethenes that hold promise for applications including super-resolution imaging.

The synthesis of a transient cationic phosphaborene [(Mes*)P=B(CAAC)]+ (Mes*=2,4,6,-tri-tert-butylphenyl, CAAC=cyclic alkylamino carbene) by halide abstraction from the B-brominated analogue is reported. This species was found to undergo rapid and selective intramolecular aliphatic C-H bond activation to yield a phosphinoborenium cation, which undergoes facile deprotonation to give a cyclic base-stabilized phosphaborene. Computational investigation of the mechanism of C-H activation indicates a boron-centred activation route with an exceptionally low barrier of 8 kJ mol-1, followed by a nearly barrierless hydride migration from boron to phosphorus. This underscores the enhanced reactivity of phosphaborenes compared to their lighter iminoborane analogues and indicates that steric stabilization alone is likely insufficient to isolate persistent cationic phosphaborenes, necessitating the use of alternative design strategies.

To model the first propagation step in the anionic polymerization of MesP═CPh 2 we studied the addition of Li[MesP(Bu)–CPh 2 ] (and related species) to nonpolymerizable H 2 C═CPh 2 . Addition proceeds via the o ‐CH 3 of the P‐Mes followed by unprecedented cyclization to C 5 P‐rings with release of Li[CHPh 2 ]. Further investigation of the aforementioned reaction using phosphaalkenes, RP═CAr 2 (R ═ Mes, m ‐Xyl; R′ ═ Ph, 4‐FC 6 H 4 , 4‐MeC 6 H 4 , 4‐MeOC 6 H 4 ), resulted in the observation of a relatively long‐lived intermediate in two instances (R ═ Mes, R’ = 4‐MeC 6 H 4 , 4‐MeOC 6 H 4 ). For the latter, the intermediate was identified as n ‐BuP(CH(4‐MeOC 6 H 4 ) 2 )[C 6 (4,6‐Me 2 )H 2 –(2‐CH 2 CH 2 CPh 2 Li) by isolation of the oxidized, H + ‐quenched product. These observations provide intriguing clues into the complex mechanism of polymerization of P ‐Mes phosphaalkenes and the chiral cyclophosphane products are of interest as ligands for catalytic applications.

To model the first propagation step in the anionic polymerization of MesP═CPh2 we studied the addition of Li[MesP(Bu)-CPh2] (and related species) to nonpolymerizable H2C═CPh2. Addition proceeds via the o-CH3 of the P-Mes followed by unprecedented cyclization to C5P-rings with release of Li[CHPh2]. Further investigation of the aforementioned reaction using phosphaalkenes, RP═CAr2 (R ═ Mes, m-Xyl; R' ═ Ph, 4-FC6H4, 4-MeC6H4, 4-MeOC6H4), resulted in the observation of a relatively long-lived intermediate in two instances (R ═ Mes, R' = 4-MeC6H4, 4-MeOC6H4). For the latter, the intermediate was identified as n-BuP(CH(4-MeOC6H4)2)[C6(4,6-Me2)H2-(2-CH2CH2CPh2Li) by isolation of the oxidized, H+-quenched product. These observations provide intriguing clues into the complex mechanism of polymerization of P-Mes phosphaalkenes and the chiral cyclophosphane products are of interest as ligands for catalytic applications.

At temperature T = 293 K, the crystal structure of CoIn2 is characterized by linear chains of equidistant Co atoms, but these chains undergo pairwise dislocation via Peierls distortion at some T > 90 K [Z. Kristallogr. 237, 239 (2022)]. Recently published differential scanning calorimetry measurements revealed at least two intervening thermodynamic effects near T-1 = 194(1) K and T-2 = 206(2) K but did not clarify how these features were related to the structural distortion or distortions. In the present paper, we report a suite of measurements on high-quality single crystals of CoIn2. We observe clear signatures of both transitions in T-dependent measurements of heat capacity, electrical resistivity, and dc magnetization. Moreover, we find a new crystal structure with polar orthorhombic space group Fdd 2 to reside between the two transitions at T = 198(2) K. Like the high-T structure, the lattice of this intermediate-T structure remains characterized by a single intrachain Co-Co distance d(Co-Co) = 2.69324(10) & Aring;, but sparse O(1%) structural disorder is resolved by the formation of a structural modulation with propagation vector q = (0, delta, 0), delta = 0.23 +/- 0.02 oriented in a direction perpendicular to the Co-Co chains. We discuss the results in light of the potential onset of a charge density wave state above the Peierls distortion.