Supramolecular Stuctures from Mononuclear, Binuclear and 2D Net of Copper(II) Complexes with 6‐Hydroxypicolinic Acid

Abstract

First examples of transition metal complexes with HpicOH [Cu(picOH)2(H2O)2] (1), [Cu(picO)(2,2′‐bpy)]·2H2O (2), [Cu(picO)(4,4′‐bpy)0.5(H2O)]n (3), and [Cu(picO)(bpe)0.5(H2O)]n (4) (HpicOH = 6‐hydroxy‐picolinic acid; 2,2′‐bpy = 2,2′‐bipyridine; 4,4′‐bpy = 4,4′‐bipyridine; bpe = 1,2‐bis(4‐pyridyl)ethane) have been synthesized and characterized by single‐crystal X‐ray diffraction. The results show that HpicOH ligand can be in the enol or ketonic form, and adopts different coordination modes under different pH value of the reaction mixture. In complex 1, HpicOH ligand is in the enol form and adopts a bidentate mode. While in complexes 2–4, as the pH rises, HpicOH ligand becomes in the ketonic form and adopts a tridentate mode. The coordination modes in complexes 1–4 have not been reported before. Because of the introduction of the terminal ligands 2,2′‐bpy, complex 2 is of binuclear species; whereas in complexes 3 and 4, picO ligands together with bridging ligands 4,4′‐bpy and bpe connect CuII ions to form 2D nets with (123)2(12)3 topology.

Syntheses, Structures and Properties of Four New Transitional Metal Complexes Based on Benzotriazole‐5‐carboxylic Acid

“…The Cu-O bond length is 1.992 Å, a little shorter than the average Cu-N bond length (2.077 Å), which is consistent with those reported for related complexes. [28] The Cu(1)…O(1a) distance is 2.812 Å, which indicates the weak interaction between the Cu(1) and O(1a). [29] So the coordination number can be described as "5＋1" for the copper(II) ion, which can be owed to the Jahn-Teller effect.…”

Disappearing and Concomitant Polymorphism of Nickel(II) Complexes with 6-Hydroxypicolinic Acid. Structural and Density Functional Theory Studies

“…17,18 The 6-OHpic ligand displays various coordination modes in lanthanide complexes, 17,18 but the N,O-chelated mode (through pyridine N atom and carboxylate O atom) is the most common one in mononuclear transition metal complexes. [11][12][13][14] Here we report the experimental geometry of orthorhombic (2) and monoclinic (3) polymorphs of [Ni(6-OHpic) 2 (py) 2 ] and [Ni(6-OHpic) 2 (py) 2 ] 3 py (4) obtained from single-crystal X-ray diffraction data and use the results of DFT calculations to interpret their relative stability. CHN analyses were performed using a Perkin-Elmer 2400 Series II CHNS analyzer in the Analytical Services Laboratories of the Ru{er Bo skovi c Institute, Zagreb, Croatia.…”

“…There are several structurally characterized transition metal and lanthanide complexes of 6-OHpicH in the literature, for example, with Cu, Co, Zn, Mn, La, Eu, Yb, and Er. Only [Cu(6-OHpic) 2 (H 2 O) 2 ], , [Cu(6-OHpic) 2 (4-pic) 2 ], and [Co(6-OHpic) 2 (4-pic) 2 ]·4-pic are mononuclear ones, with two N , O -bidentate 6-OHpic ligands and two water or 4-picoline molecules in trans position, respectively. Other Cu complexes with 6-OHpic are binuclear (with 2,2′-bipyridine as an additional ligand) or polynuclear (with 4,4′-bipyridine or 1,2-bis(4-pyridyl)ethane as additional ligands) .…”

“…Only [Cu(6-OHpic) 2 (H 2 O) 2 ], , [Cu(6-OHpic) 2 (4-pic) 2 ], and [Co(6-OHpic) 2 (4-pic) 2 ]·4-pic are mononuclear ones, with two N , O -bidentate 6-OHpic ligands and two water or 4-picoline molecules in trans position, respectively. Other Cu complexes with 6-OHpic are binuclear (with 2,2′-bipyridine as an additional ligand) or polynuclear (with 4,4′-bipyridine or 1,2-bis(4-pyridyl)ethane as additional ligands) . Zinc complexes with 6-OHpic and 2,2′-bipyridine, 1,10′-phenantroline or 1,2-bis(4-pyridyl)ethane are polynuclear, the manganese complex with 6-OHpic and pyridine is binuclear, while lanthanide (La, Eu, Yb, Er) complexes are exclusively polynuclear. , The 6-OHpic ligand displays various coordination modes in lanthanide complexes, , but the N , O -chelated mode (through pyridine N atom and carboxylate O atom) is the most common one in mononuclear transition metal complexes. − …”