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The preparations, photophysical and electrochemical properties of a series of fac‐[Re(CO)$_{3}$(diimine)Br] complexes are presented. The bipyridine (bpy) based diimine ligands feature symmetrical and asymmetrical 3,3’‐diamino‐2,2’‐bipyridine substitution patterns. Photophysical and electrochemical properties of these complexes are tunable, depending on their organic diimine framework. Introduction of a distal urea bridge via the 3,3’‐substitution pattern led to prolonged phosphorescence lifetimes without a significant change in absorbance and phosphorescence emission wavelengths. Reversible electrochemical bipyridine reduction remained largely unchanged by this derivatization.

The fac–mer isomerisation in [MX$_{3}$(CO)$_{3}$]$^{2−}$ (M = Re, $^{99}$Tc) is induced by a PNP pincer-type ligand in the presence of a halide scavenger. The adaptation to the aqueous and saline chemistry of $^{99m}$Tc yields mer-[$^{99m}$Tc(PNP)(CO)$_{3}$]$^{+}$.

Metal–ligand cooperativity is a powerful tool for the activation of various bonds but has rarely, if ever, been studied with the radioactive transition metal $^{\text{99}}$Tc. In this work, we explore this bond activation pathway with the dearomatized PNP complex cis-[99TcI(PyrPNPtBu*)(CO)2] (4), which was synthesized by deprotonation of trans-[99TcI(PyrPNPtBu)(CO)2Cl] with KOtBu. Analogous to its rhenium congener, the dearomatized compound reacts with CO2 to form the carboxy complex cis-[99TcI(PyrPNPtBu–COO)(CO)2] and with H2 to form the mono-hydride complex cis-[99TcI(PyrPNPtBu)(CO)2H] (7). Substrates with weakly acidic protons are deprotonated by the Brønsted basic pincer backbone of 4, yielding a variety of intriguing complexes. Reactions with terminal alkynes enable the isolation of acetylide complexes. The deprotonation of an imidazolium salt results in the in situ formation and coordination of a carbene ligand. Furthermore, a study with heterocyclic substrates allowed for the isolation of pyrrolide and pyrazolide complexes, which is uncommon for Tc. The spectroscopic analyses and their solid-state structures are reported.

The title compound, C10H13N5O4.2C2H6OS, which is of interest with respect to its biological activity, at 183 K has orthorhombic P212121 crystal symmetry. The structure displays a network of intermolecular N—H...N, N—H...O and O—H...O hydrogen bonds. 2′-Deoxyguanosine molecules are linked to each other and to the two dimethyl sulfoxide solvent molecules by hydrogen bonding.

Two-dimensional (2D) materials are a key target for many applications in the modern day. Self-assembly is one approach that can bring us closer to this goal, which usually relies upon strong, directional interactions instead of covalent bonds. Control over less directional forces is more challenging and usually does not result in as well-defined materials. Explicitly incorporating topography into the design as a guiding effect to enhance the interacting forces can help to form highly ordered structures. Herein, we show the process of shape-assisted self-assembly to be consistent across a range of derivatives that highlights the restriction of rotational motion and is verified using a diverse combination of solid state analyses. A molecular curvature governed angle distribution nurtures monomers into loose columns that then arrange to form 2D structures with long-range order observed in both crystalline and soft materials. These features strengthen the idea that shape becomes an important design principle leading towards precise molecular self-assembly and the inception of new materials.

Phthalocyanines are ideal candidates as photosensitizers for photodynamic therapy (PDT) of cancer due to their favorable chemical and photophysical properties. However, their tendency to form aggregates in water reduces PDT efficacy and poses challenges in obtaining efficient forms of phthalocyanines for therapeutic applications. In the current work, polyvinylpyrrolidone (PVP) and micellar formulations were compared for encapsulating and monomerizing a water-soluble zinc phthalocyanine bearing four non-peripheral triethylene glycol chains (Pc1). 1H NMR spectroscopy combined with UV–vis absorption and fluorescence spectroscopy revealed that Pc1 exists as a mixture of regioisomers in monomeric form in dimethyl sulfoxide but forms dimers in an aqueous buffer. PVP, polyethylene glycol castor oil (Kolliphor RH40), and three different triblock copolymers with varying proportions of polyethylene and polypropylene glycol units (termed P188, P84, and F127) were tested as micellar carriers for Pc1. 1H NMR chemical shift analysis, diffusion-ordered spectroscopy, and 2D nuclear Overhauser enhancement spectroscopy was applied to monitor the encapsulation and localization of Pc1 at the polymer interface. Kolliphor RH40 and F127 micelles exhibited the highest affinity for encapsulating Pc1 in the micellar core and resulted in intense Pc1 fluorescence emission as well as efficient singlet oxygen formation along with PVP. Among the triblock copolymers, efficiency in binding and dimer dissolution decreased in the order F127 > P84 > P188. PVP was a strong binder for Pc1. However, Pc1 molecules are rather surface-attached and exist as monomer and dimer mixtures. The results demonstrate that NMR combined with optical spectroscopy offer powerful tools to assess parameters like drug binding, localization sites, and dynamic properties that play key roles in achieving high host–guest compatibility. With the corresponding adjustments, polymeric micelles can offer simple and easily accessible

Here, we report six novel, easily accessible BODIPY-based agents for cancer treatment. In contrast to established photodynamic therapy (PDT) agents, these BODIPY-based compounds show additional photothermal activity and their cytotoxicity is not dependent on the generation of reactive oxygen species (ROS). The agents show high photocytotoxicity upon irradiation with light and low dark toxicity in different cancer cell lines in 2D culture as well as in 3D multicellular tumor spheroids (MCTSs). The ratio of dark to light toxicity (phototoxic index, PI) of these agents reaches striking values exceeding 830,000 after irradiation with energetically low doses of light at 630 nm. The oxygen-dependent mechanism of action (MOA) of established photosensitizers (PSs) hampers effective clinical deployment of these agents. Under hypoxic conditions (0.2% O2), which are known to limit the efficiency of conventional PSs in solid tumors, photocytotoxicity was induced at the same concentration levels, indicating an oxygen-independent photothermal MOA. With a PI exceeding 360,000 under hypoxic conditions, both PI values are the highest reported to date. We anticipate that small molecule agents with a photothermal MOA, such as the BODIPY-based compounds reported in this work, may overcome this barrier and provide a new avenue to cancer therapy.

Exploration of new organometallic systems based on polyhedral boron clusters has the potential to solve challenging chemical problems such as the stabilization of reactive intermediates and transition-state-like species postulated for E–H (E = H, B, C, Si) bond activation reactions. We report on facile and clean B–H activation of a hydroborane by a new iridium boron cluster complex. The product of this reaction is an unprecedented and fully characterized transition metal-stabilized boron cation or borenium. Moreover, this intermediate bears an unusual intramolecular B···H interaction between the hydrogen originating from the activated hydroborane and the cyclometallated metal-bonded boron atom of the boron cluster. This B···H interaction is proposed to be an arrested insertion of hydrogen into the Bcage–metal bond and the initiation step for iridium “cage-walking” around the upper surface of the boron cluster. The “cage-walking” process is supported by the hydrogen–deuterium exchange observed at the boron cluster, and a mechanism is proposed on the basis of theoretical methods with a special focus on the role of noncovalent interactions. All new compounds were isolated and fully characterized by NMR spectroscopy and elemental analysis. Key compounds were studied by single crystal X-ray diffraction and X-ray photoelectron spectroscopy.

The tetratopic 1,4-bis(2-phenylethoxy)-2,5-bis(3,2′:6′,3′′-terpyridin-4′-yl)benzene (1) and 1,4-bis(3-phenylpropoxy)-2,5-bis(3,2′:6′,3′′-terpyridin-4′-yl)benzene (2) ligands have been prepared and fully characterised. Combination of ligand 1 or 2 and [M(hfacac)2]·xH2O (M = Cu, x = 1; M = Zn, x = 2) under conditions of crystal growth by layering led to the formation of [Cu2(hfacac)4(1)]n·3.6n(1,2-Cl2C6H4)·2nCHCl3, [Zn2(hfacac)4(1)]n·nMeC6H5·1.8nCHCl3, [Cu2(hfacac)4(2)]n·nMeC6H5·2nH2O, [Cu2(hfacac)4(2)]n·2.8nC6H5Cl and [Cu2(hfacac)4(2)]n·2n(1,2-Cl2C6H4)·0.4nCHCl3·0.5nH2O. For each compound, single-crystal X-ray analysis revealed the assembly of a planar (4,4)-net in which the tetratopic ligands 1 or 2 define the nodes. The metal centres link two different bis(3,2′:6′,3′′-tpy) ligands via the outer pyridine rings; whereas copper(II) has N-donors in a trans-arrangement, zinc(II) has them in cis. This difference between the copper(II) and zinc(II) coordination polymers modifies the architecture of the assembly without changing the underlying (4,4)-network.

A series of structurally related, acyclic cobalt tetrapyridyl hydrogen evolving catalysts (HEC) were prepared and characterized. The common motif, di(2,2′-bipyridin-6-yl)-methane, was derivatized at the bridging methylene to include a carbonyl group (L1), a hydroxy (L2), a methyl and a hydroxy (L3), a 1,1′-biphenyl-2,2′-diyl (L4), a hydroxy and a phenyl (L5) or a hydroxy and a pyrid-6-yl group. These catalysts were compared with the known HEC [Co(appy)Br]Br. Photo- and electrochemistry showed a distinct influence of the bridging position on rates and stabilities of the hydrogen evolution reaction (HER). Apolar ligands resulted in inferior catalytic performance as compared to HECs with polar substituents. Electrochemically, [Co(L1)Br2] was shown to be converted to [Co(L2)Br2] in catalysis. The best catalyst made more than 10’000 turnovers, albeit at an overpotential of 600 mV. Additional pH dependent mechanistic aspects were elucidated by cyclic voltammetry.

The identification of an alternative chemical space in order to address the global challenge posed by emerging antimicrobial resistance is very much needed for the discovery of novel antimicrobial lead compounds. Boron clusters are currently being explored in drug discovery due to their unique steric and electronic properties. However, the challenges associated with the synthesis and derivatization techniques of these compounds have limited their utility in the rapid construction of a library of molecules for screening against various biological targets as an alternative molecular platform. Herein, we report a transition-metal-catalyzed regioselective direct B–H alkylation–annulation of the closo-dodecaborate anion with natural products such as menthol and camphor as the directing groups. This method allowed the rapid construction of a library of 1,2,3-trisubstituted clusters, which were evaluated in terms of their antibacterial activity against WHO priority pathogens. Several of the synthesized dodecaborate derivatives displayed medium- to high-level bactericidal activity against Gram-positive and Gram-negative bacteria.