Novel Copper(II) Induced Formation of a Porphyrinogen Derivative:  X-ray Structural, Spectroscopic, and Electrochemical Studies of Porphyrinogen Complexes of Cu(II) and Co(III) Complex of a Trispyrazolyl Tripodal Ligand

Abstract

Copper(II) complexes of a novel pyrazole containing porphyrinogen and cobalt(III) and zinc(II) complexes of a pyrazole containing tripodal ligand having N-donor atoms have been investigated. 5-Methyl-3-formylpyrazole (MPA) on reaction with copper(II) nitrate or perchlorate in the presence of tris(2-aminoethyl)amine (tren) forms novel pyrazole-based porphyrinogen complexes [Cu(T(3)-porphyrinogen)(H(2)O)](NO(3))(2) (1a) and [Cu(T(3)-porphyrinogen)(H(2)O)](ClO(4))(2) (1b) where T(3)-porphyrinogen is 1,6,11,16-tetraaza-5,10,15,20-tetrahydroxy-2,7,12,17-tetramethylporphyrinogen. The same products are also obtained when tren is replaced by triethylamine. By contrast, the reaction between MPA, tren, and cobalt(II) perchlorate produces the cobalt(III) complex [Co(HMPz(3)tren)]ClO(4) (2) derived from the tripodal Schiff base tris[4-(3-(5-methyl-pyrazolyl)-3-aza-3-butenyl]amine (H(3)MPz(3)tren). The X-ray crystal structures of the copper(II) complexes (1a and 1b) and the cobalt(III) complex (2) have been determined. The structures show distorted square pyramidal coordination environments for 1a and 1b with the water molecule occupying the apical site, while for complex 2 a distorted octahedral geometry is obtained. Data for 1a follow: a = 19.476(3) A, b = 9.4116(8) A, c = 14.204(3) A; alpha = 90 degrees = gamma, beta = 107.58(2) degrees; V = 2482.0(7) A(3), Z = 4. Data for 1b follow: a = 20.967(3) A, b = 9.1563(18) A, c = 14.858(4) A; alpha = 90 degrees = gamma, beta = 108.44(3) degrees; V = 2706.0(10) A(3), Z = 4. Data for 2 follow: a = 21.293(3) A, b = 12.724(2) A, c = 19.777(4) A; alpha = 90 degrees = gamma, beta = 93.03(2) degrees; V = 5350.6(15) A(3), Z = 8. All three complexes crystallize in the monoclinic crystal system with the C2/c space group. The complexes are further characterized by UV-vis, IR, EPR, and electrochemical studies.

5-Chlorosalicylaldehyde salicylhydrazone

“…Schiff base compounds have been of great interest for a long time and have played an important role in the development of coordination chemistry (Musie et al, 2001;Bernardo et al, 1996;Paul et al, 2002). As an extension of work on the structural characterization of such compounds, the crystal structure of the title compound, (I), is reported here.…”

2,4-Dibromo-6-(4-methylpyridin-2-yliminomethyl)phenol

“…Schiff base compounds have been of great interest for a long time. These compounds have played an important role in the development of coordination chemistry (Bernardo et al, 1996;Musie et al, 2001;Paul et al, 2002). As an extension of work on the structural characterization of such compounds, the crystal structure of the title compound, (I), is reported here (Fig.…”

Use of Pyrazole Hydrogen Bonding in Tripodal Complexes to Form Self Assembled Homochiral Dimers

“…[Co(tren(MepyrzH) 3 ](ClO 4 ) 3 A solution of HCl (1.32 mL of 0.1 M HCl in methanol, 0.132 mmol) was added to a slurry of the previously prepared [32] Cotren(Mepyrz) 3 [33]. Tren (0.077 g, 0.53 mmol) and absolute ethanol (~16 mL) were added to a 25 mL round bottom flask.…”

“…The product is a cobalt(II)-cobalt(III) mixed valence species [38], [Cotren(MePyrzH) 3 ][Cotren(MePyrz) 3 ]I 2 . The likely sequence of reactions is protonation of the cobalt complex by the ammonium cation, followed by reduction of this species by iodide and the formation of the pseudo dimer as illustrated below: For completeness an attempt was made to prepare the previously synthesized [33] and structurally characterized [39]. For [Cotren(Mepyrz) 3 ] the absorption appears close to 1600 cm −1 , consistent with deprotonation of the ligand.…”