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1. Picosecond to Nanosecond Manipulation of Excited-State Lifetimes in Complexes with an Fe II to Ti IV Metal-to-Metal Charge Transfer: The Role of Ferrocene Centered Excited States

   https://doi.org/10.1021/acs.inorgchem.9b02316  

   Livshits, Maksim Y. ; Turlington, Michael D. ; Trindle, Carl O. ; Wang, Lei ; Altun, Zikri ; Wagenknecht, Paul S. ; Rack, Jeffrey J. ( November 2019 , Inorganic Chemistry)
2. “Off‐Label Use” of the Siderophore Enterobactin Enables Targeted Imaging of Cancer with Radioactive Ti (IV)

   https://doi.org/10.1002/ange.202319578  

   Koller, Angus J. ; Glaser, Owen ; DeLuca, Molly C. ; Motz, Rachel N. ; Amason, Edith K. ; Carbo‐Bague, Imma ; Mixdorf, Jason C. ; Guzei, Ilia A. ; Aluicio‐Sarduy, Eduardo ; Śmiłowicz, Dariusz ; et al ( March 2024 , Angewandte Chemie)

   The development of inert, biocompatible chelation methods is required to harness the emerging positron emitting radionuclide⁴⁵Ti for radiopharmaceutical applications. Herein, we evaluate the Ti^(IV)‐coordination chemistry of four catechol‐based, hexacoordinate chelators using synthetic, structural, computational, and radiochemical approaches. The siderophore enterobactin (Ent) and its synthetic mimic TREN‐CAM readily form mononuclear Ti^(IV)species in aqueous solution at neutral pH. Radiolabeling studies reveal that Ent and TREN‐CAM form mononuclear complexes with the short‐lived, positron‐emitting radionuclide⁴⁵Ti^(IV), and do not transchelate to plasma proteins in vitro and exhibit rapid renal clearance in naïve mice. These features guide efforts to target the⁴⁵Ti isotope to prostate cancer tissue through the design, synthesis, and evaluation of Ent‐DUPA, a small molecule conjugate composed of a prostate specific membrane antigen (PSMA) targeting peptide and a monofunctionalized Ent scaffold. The [⁴⁵Ti][Ti(Ent‐DUPA)]²⁻complex forms readily at room temperature. In a tumor xenograft model in mice, selective tumor tissue accumulation (8±5 %,n=5), and low off‐target uptake in other organs is observed. Overall, this work demonstrates targeted imaging with⁴⁵Ti^(IV), provides a foundation for advancing the application of⁴⁵Ti in nuclear medicine, and reveals that Ent can be repurposed as a⁴⁵Ti‐complexing cargo for targeted nuclear imaging applications.

    

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3. “Off‐Label Use” of the Siderophore Enterobactin Enables Targeted Imaging of Cancer with Radioactive Ti (IV)

   https://doi.org/10.1002/anie.202319578  

   Koller, Angus J. ; Glaser, Owen ; DeLuca, Molly C. ; Motz, Rachel N. ; Amason, Edith K. ; Carbo‐Bague, Imma ; Mixdorf, Jason C. ; Guzei, Ilia A. ; Aluicio‐Sarduy, Eduardo ; Śmiłowicz, Dariusz ; et al ( March 2024 , Angewandte Chemie International Edition)

   The development of inert, biocompatible chelation methods is required to harness the emerging positron emitting radionuclide⁴⁵Ti for radiopharmaceutical applications. Herein, we evaluate the Ti^(IV)‐coordination chemistry of four catechol‐based, hexacoordinate chelators using synthetic, structural, computational, and radiochemical approaches. The siderophore enterobactin (Ent) and its synthetic mimic TREN‐CAM readily form mononuclear Ti^(IV)species in aqueous solution at neutral pH. Radiolabeling studies reveal that Ent and TREN‐CAM form mononuclear complexes with the short‐lived, positron‐emitting radionuclide⁴⁵Ti^(IV), and do not transchelate to plasma proteins in vitro and exhibit rapid renal clearance in naïve mice. These features guide efforts to target the⁴⁵Ti isotope to prostate cancer tissue through the design, synthesis, and evaluation of Ent‐DUPA, a small molecule conjugate composed of a prostate specific membrane antigen (PSMA) targeting peptide and a monofunctionalized Ent scaffold. The [⁴⁵Ti][Ti(Ent‐DUPA)]²⁻complex forms readily at room temperature. In a tumor xenograft model in mice, selective tumor tissue accumulation (8±5 %,n=5), and low off‐target uptake in other organs is observed. Overall, this work demonstrates targeted imaging with⁴⁵Ti^(IV), provides a foundation for advancing the application of⁴⁵Ti in nuclear medicine, and reveals that Ent can be repurposed as a⁴⁵Ti‐complexing cargo for targeted nuclear imaging applications.

    

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4. Complexes of [(dadi)Ti(L/X)] m That Reveal Redox Non-Innocence and a Stepwise Carbene Insertion into a Carbon–Carbon Bond

   https://doi.org/10.1021/acs.organomet.8b00188  

   Heins, Spencer P. ; Morris, Wesley D. ; Cundari, Thomas R. ; MacMillan, Samantha N. ; Lobkovsky, Emil B. ; Livezey, Nicholas M. ; Wolczanski, Peter T. ( June 2018 , Organometallics)
5. Comparison of two Mn IV Mn IV -bis-μ-oxo complexes {[Mn IV (N 4 (6-Me-DPEN))] 2 (μ-O) 2 } 2+ and {[Mn IV (N 4 (6-Me-DPPN))] 2 (μ-O) 2 } 2+

   https://doi.org/10.1107/S2056989020004557  

   Coggins, Michael K. ; Downing, Alexandra N. ; Kaminsky, Werner ; Kovacs, Julie A. ( July 2020 , Acta Crystallographica Section E Crystallographic Communications)

   null (Ed.)

   The addition of tert -butyl hydroperoxide ( t BuOOH) to two structurally related Mn II complexes containing N,N -bis(6-methyl-2-pyridylmethyl)ethane-1,2-diamine (6-Me-DPEN) and N,N -bis(6-methyl-2-pyridylmethyl)propane-1,2-diamine (6-Me-DPPN) results in the formation of high-valent bis-oxo complexes, namely di-μ-oxido-bis{[ N , N -bis(6-methyl-2-pyridylmethyl)ethane-1,2-diamine]manganese(II)}( Mn — Mn ) bis(tetraphenylborate) dihydrate, [Mn(C 16 H 22 N 4 ) 2 O 2 ](C 24 H 20 B) 2 ·2H 2 O or {[Mn IV (N 4 (6-Me-DPEN))] 2 ( μ -O) 2 }(2BPh 4 )(2H 2 O) ( 1 ) and di-μ-oxido-bis{[ N , N -bis(6-methyl-2-pyridylmethyl)propane-1,3-diamine]manganese(II)}( Mn — Mn ) bis(tetraphenylborate) diethyl ether disolvate, [Mn(C 17 H 24 N 4 ) 2 O 2 ](C 24 H 20 B) 2 ·2C 4 H 10 O or {[Mn IV (N 4 (6-MeDPPN))] 2 ( μ -O) 2 }(2BPh 4 )(2Et 2 O) ( 2 ). Complexes 1 and 2 both contain the `diamond core' motif found previously in a number of iron, copper, and manganese high-valent bis-oxo compounds. The flexibility in the propyl linker in the ligand scaffold of 2 , as compared to that of the ethyl linker in 1 , results in more elongated Mn—N bonds, as one would expect. The Mn—Mn distances and Mn—O bond lengths support an Mn IV oxidation state assignment for the Mn ions in both 1 and 2 . The angles around the Mn centers are consistent with the local pseudo-octahedral geometry. 

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