کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1338857 979683 2007 12 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Syntheses, structures and hydrolytic properties of copper(II) complexes of asymmetrically N-functionalised 1,4,7-triazacyclononane ligands
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی معدنی
پیش نمایش صفحه اول مقاله
Syntheses, structures and hydrolytic properties of copper(II) complexes of asymmetrically N-functionalised 1,4,7-triazacyclononane ligands
چکیده انگلیسی

A series of new asymmetrically N-substituted derivatives of the 1,4,7-triazacyclononane (tacn) macrocycle have been prepared from the common precursor 1,4,7-triazatricyclo[5.2.1.04,10]decane: 1-ethyl-4-isopropyl-1,4,7-triazacyclononane (L1), 1-isopropyl-4-propyl-1,4,7-triazacyclononane (L2), 1-(3-aminopropyl)-4-benzyl-7-isopropyl-1,4,7-triazacyclononane (L3), 1-benzyl-4-isopropyl-1,4,7-triazacyclononane (L4) and 1,4-bis(3-aminopropyl)-7-isopropyl-1,4,7-triazacyclononane (L5). The corresponding monomeric copper(II) complexes were synthesised and were found to be of composition: [Cu(L1)Cl2] · 1/2 H2O (C1), [Cu(L4)Cl2] · 4H2O (C2), [Cu(L3)(MeCN)](ClO4)2 (C3), [Cu(L5)](ClO4)2 · MeCN · NaClO4 (C4) and [Cu(L2)Cl2] · 1/2 H2O (C5). The X-ray crystal structures of each complex revealed a distorted square-pyramidal copper(II) geometry, with the nitrogen donors on the ligands occupying 3 (C1 and C2), 4 (C3) or 5 (C4) coordination sites on the Cu(II) centre. The metal complexes were tested for the ability to hydrolytically cleave phosphate esters at near physiological conditions, using the model phosphodiester, bis(p-nitrophenyl)phosphate (BNPP). The observed rate constants for BNPP cleavage followed the order kC1 ≈ kC2 > kC5 ≫ kC3 > kC4, confirming that tacn-type Cu(II) complexes efficiently accelerate phosphate ester hydrolysis by being able to bind phosphate esters and also form the nucleophile necessary to carry out intramolecular cleavage. Complexes C1 and C2, featuring asymmetrically disubstituted ligands, exhibited rate constants of the same order of magnitude as those reported for the Cu(II) complexes of symmetrically tri-N-alkylated tacn ligands (k ∼ 1.5 × 10−5 s−1).

A series of square-pyramidal copper(II) complexes of N-alkylated derivatives of 1,4,7-triazacyclononane (L1–L5) are reported whose ability to effectively cleave phosphate diesters decreases with the number of copper(II) coordination sites occupied by the ligand.Figure optionsDownload as PowerPoint slide

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Polyhedron - Volume 26, Issue 2, 22 January 2007, Pages 344–355
نویسندگان
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