Single versus Double Cu(I) Catalyzed [3 + 2] Azide/Platinum Diacetylide Cycloaddition Reactions

Electrospray Mass Spectrometry to Study Combinatorial iClick Reactions and Multiplexed Kinetics of [Ru(N3)(N∧N)(terpy)]PF6 with Alkynes of Different Steric and Electronic Demand

In a combinatorial approach, a family of ruthenium(II) azido complexes [Ru(N₃)(N∧N)(terpy)]PF₆ with terpy = 2,2':6',2″-terpyridine and N∧N as a bidentate chelator derived from 2,2'-biypridine and its 4,4'-disubstituted derivatives, 2,2'-bipyrimidine, and 1,10-phenanthroline were reacted with different internal and terminal alkynes to give access to a total of 7 × 7 = 49 triazolato complexes in a room-temperature catalyst-free iClick reaction. The reactants were mixed in a repurposed high-performance liquid chromatography (HPLC) autosampler, and the reaction progress was monitored by direct injection into an electrospray mass spectrometer. The ratio of the peak intensities of [Ru(N₃)(N∧N)(terpy)]⁺ and [Ru(triazolato)(N∧N)(terpy)]⁺ was converted to a colored heat map for facile visual inspection of the conversion ratio. By automated multiple injections of the reaction mixture in fixed time intervals and plotting peak intensities over reaction time, pseudo-first-order rate constants were easily determined. Finally, nonoverlapping isotope patterns of the azido starting materials and triazolato products enabled multiplexed parallel determination of rate constants for four different ruthenium(II) azido complexes from a single sample vial, thereby reducing experiment time by 75%.

iClick synthesis of network metallopolymers

Described is an approach to preparing the first iClick network metallopolymers with porous properties. Treating digoldazido complex 2-AuN3 with trigoldacetylide 3-AuPPh3 or 3-AuPEt3, trialkyne 3-H, tetragoldacetylide 4-AuPPh3, or tetraalkyne 4-H in CH₂Cl₂ affords five iClick network metallopolymers 5-AuPPh3, 5-AuPEt3, 5-H, 6-AuPPh3, and 6-H. Confirmation of the iClick network metallopolymers comes from FTIR, ¹³C solid-state cross-coupling magic angle spinning (CPMAS) NMR spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and nitrogen and CO₂ sorption analysis. Employing model complexes 7-AuPPh3, 7-AuPEt3, 7-H, 8-AuPPh3, and 8-H provides structural insights due to the insolubility of iClick network metallopolymers.

Trapping of Terminal Platinapolyynes by Copper(I) Catalyzed Click Cycloadditions; Probes of Labile Intermediates in Syntheses of Complexes with Extended sp Carbon Chains, and Crystallographic Studies

The silylated hexatriynyl complex trans-(C₆ F₅ )(p-tol₃ P)₂ Pt(C≡C)₃ SiEt₃ (PtC₆ TES) is converted in situ to PtC₆ H (wet n-Bu₄ N⁺ F^- , THF) and cross coupled with the diyne H(C≡C)₂ SiEt₃ (HC₄ TES; CuCl/TMEDA, O₂ ) to give PtC₁₀ TES (71 %). This sequence is repeated twice to afford PtC₁₄ TES (65 %) and then PtC₁₈ TES (27 %). An analogous series of reactions starting with PtC₈ TES gives PtC₁₂ TES (60 %), then PtC₁₆ TES (43 %), and then PtC₂₀ TES (17 %). Similar cross couplings with H(C≡C)₂ Si(i-Pr)₃ (HC₄ TIPS) give PtC₁₂ TIPS (68 %), PtC₁₄ TIPS (68 %), and PtC₁₆ TIPS (34 %). The trialkylsilyl species (up to PtC₁₈ TES) are converted to 3+2 "click" cycloadducts or 1,4-disubstituted 1,2,3-triazoles trans-(C₆ F₅ )(p-tol₃ P)₂ Pt(C≡C)_n-1 C=CHN(CH₂ C₆ H₅ )N=N (29-92 % after workups). The most general procedure involves generating the terminal polyynes PtC_x H (wet n-Bu₄ N⁺ F^- , THF) in the presence of benzyl azide in DMF and aqueous CuSO₄ /ascorbic acid. All of the preceding complexes are crystallographically characterized and the structural and spectroscopic properties analyzed as a function of chain length. Two pseudopolymorphs of PtC₂₀ TES are obtained, both of which feature molecules with parallel sp carbon chains in a pairwise head/tail packing motif with extensive sp/sp van der Waals contacts.

Exploiting azide-alkyne click chemistry in the synthesis, tracking and targeting of platinum anticancer complexes

Click chemistry is fundamentally important to medicinal chemistry and chemical biology. It represents a powerful and versatile tool, which can be exploited to develop novel Pt-based anticancer drugs and to better understand the biological effects of Pt-based anticancer drugs at a cellular level. Innovative azide-alkyne cycloaddition-based approaches are being used to functionalise Pt-based complexes with biomolecules to enhance tumour targeting. Valuable information in relation to the mechanisms of action and resistance of Pt-based drugs is also being revealed through click-based detection, isolation and tracking of Pt drug surrogates in biological and cellular environments. Although less well-explored, inorganic Pt-click reactions enable synthesis of novel (potentially multimetallic) Pt complexes and provide plausible routes to introduce functional groups and monitoring Pt-azido drug localisation.

An Application Exploiting Aurophilic Bonding and iClick to Produce White Light Emitting Materials

The paper focuses on exploiting aurophilic bonding to produce white light emitting materials. Inorganic Click (iClick) is employed to link two or four Au(I) metal ions through a triazolate bridge. Depending on the choice of phosphine ligand (PEt₃ or PPh₃), dinuclear Au₂-FO or tetranuclear Au₄-FO complexes can be controllably synthesized (FO = 2-(9,9-dioctylfluoreneyl-)). The iClick products Au₂-FO and Au₄-FO are characterized by combustion analysis and multinuclear NMR, TOCSY 1D, ¹H-¹³C gHMBC, and ¹H-¹³C gHSQC. In addition, the photophysical properties of Au₂-FO and Au₄-FO were examined in THF solution. Transient absorption spectroscopy was employed to elucidate the excited state features of the gold compounds. Solution processed OLEDs were fabricated and characterized, which gave white light electroluminescence with CIE coordinates (0.34, 0.36), as seen referenced to CIE standard illuminant D65 (0.31, 0.32). TDDFT computational analysis of Au₂-FO and Au₄-FO reveals the origin of light emission. In the case of Au₄-FO, direct excitation leads to increased aurophilic bonding in the excited state, and as a result the emission profile is broadened to cover a larger region of the visible spectrum, thus giving white light emission. Designing molecules that can access or increase aurophilic bonding in the excited state provides another tool for fine-tuning the emission profiles of gold complexes.

A new synthetic route to in-chain metallopolymers via copper(i) catalyzed azide-platinum-acetylide iClick

The first example of an in-chain metallo-poly(triazolate) synthesized by CuAAC is reported. Azido-platinum-acetylide (A-M-B) monomers are catalytically polymerized with copper(i) acetate to yield 1,2,3-triazolate linked Pt(ii) units. The metallopolymers are characterized by multinuclear NMR, IR, UV/Vis, GPC, and MS.