Research Topics

Organometallic Plastic Crystals

Organometallic Plastic Crystals

While plastic crystals (dynamically-orientationally disordered mesogens) are so far rare in organometallic chemistry, we discovered that formally five-coordinate ionic Ni(II) complexes [(π-allyl)NiL₃]Y and neutral M(I) complexes (π-allyl)ML₃ (M = Co, Rh, Ir) with L = PMe₃, P(OMe)₃, and other ligands undergo a phase transition from the ordered to a plastic phase. The plastic properties arise from mobility of the π-allyl group in the solid-state. For the ionic Ni compounds, besides motion of the anions Y, the cations appear to tumble on their site in the lattice, whereas the neutral M(I) complexes rotate about an axis. For recrystallization, some compounds require partial ordering in a glassy-crystalline state.

Cisplatin-related Metal Complexes

Cisplatin-related Metal Complexes

Among the most prominent anti-cancer drugs are cisplatin, carboplatin, and oxaliplatin. Therapy with these drugs is frequently associated with serious side-effects, and inherent or acquired platinum resistance is a major problem. Thus, there is an unabated need for remedy and probing new structures. We have studied parent bispidine (3,7-diazabicyclo[3.3.1]nonane, C₇H₁₄N₂) and its derivatives, substituted at the remote 9-position, for usage as “carrier ligands” for Pt(II). The studies allow insight into parameters such as hydrogen-bonding, association, hydration, water solubility, and polarity of the complexes, relevant to cytostatic potency.

 

Cesium Chemistry

Cesium Chemistry

The cesium cation, Cs⁺, is the largest and least electrophilic singly charged metal ion. Isolation of Cs⁺ salts from aqueous solutions represents a problem in many areas, as there are (a) exploitation of cesium from minerals, (b) reprocessing of nuclear fuels and separation of the strong gamma emitter ¹³⁷Cs, (c) decontamination of ¹³⁷Cs containing waste solutions, and (d) preparation of ^131/137Cs radioactive probes for a variety of applications. We have found that the fluorinated aryl boronate (FAB) anion [H₂NB₂(C₆F₅)₆]^– allows for 100% selective and quantitative separation of Cs⁺ from any aqueous solution, affording insoluble Cs[H₂NB₂(C₆F₅)₆]. The high specificity for Cs⁺ arises from the specific conformation of the anion which is exclusively present in Cs[H₂NB₂(C₆F₅)₆]. Thereby, Cs⁺ is bonded to five anions in a 3D lattice, and the unprecedented coordination number CN = 16 is reached, allowing for enhanced stability of the lattice.

 

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