Synthesis and characterization of a ladder-like structure compound formed by cadmium ( II ) and anionic nitronyl nitroxide

A ladder-like structure compound formed by cadmium (II) and anionic nitronyl nitroxide, [Cd2(NITpBA)4(H2O)4] (where NITpBA = 2-(4-carboxyphenyl)4,4,5,5-tetramethyl-4,5-dihydro-imidazol1-oxyl-3-oxide), has been synthesized and characterized. X-ray analysis reveals that the compound 1 crystallizes in the monoclinic P21/c (No. 14) space group, and [Cd2(NITpBA)4(H2O)4] units are linked into infinite chains by radical bridging ligands.


INTRODUCTION
The field of molecule-based materials has attracted intense interest for decades [1].The design and synthesis molecular-based magnetic materials by using metalradical approach have become one of the very promising strategies [2].The organic radicals can act as not only spin carriers but also building blocks.In this field, the increasing attention has been focused on the coordination complexes of paramagnetic metal ions with organic radical ligands in order to exploit new molecular magnetic materials and diverse topological structures [3,4].The possibility to play with anionic nitronyl nitroxides increases the chances for designing magnetic molecular materials and diverse structures [5,6].The stable anionic radical NITpBAH, named as 2-(4-carboxyphenyl)-4,4, 5,5-teramethyl-4,5-dihydro1H-imidazol-1-oxyl-3-oxide, has two different types of potentially metal-coordinating site.One is the carboxylate group; the other consists of the two oxygen atoms belonging to the nitronyl nitroxide part.Recently, due to the increased recognition of its role in biological organisms, there has been an increasing interest in the coordination chemistry of cadmium [7].

Materials and Measurements
All chemicals used were of reagent grade and used without further purification.The NITPBA was prepared by the literature method [8].Elemental analysis for carbon, hydrogen and nitrogen were carried out on a Perkin-Elmer elemental analyzer model 240.The IR spectrum was taken on a Shimadzu 408 IR spectrophotometer in the 4000 -400 cm −1 region with KBr pellets.
A dark blue crystal with dimensions 0.20 × 0.20 × 0.20 mm 3 was mounted on a glass fiber in a random orientation.The determination of the unit cell and data collection was performed on a computer-controlled Bruker APEX-II CCD diffractometer.3635 independent reflections [R(int) = 0.0203] in the range 1.63˚ ≤ θ ≤ 28.35˚ with −18≤ h ≤ 18, −12 ≤ k ≤ 11, −12 ≤ l ≤ 16 were collected by using an φ -ω scan technique at 293(2) K using Mo-Kα radiation with a graphite monochromator (λ = 0.71073A).The X-ray structure analysis revealed that the compound belongs to the monoclinic system, space group P2 1 /c.Absorption corrections were applied using SADABS program.The structure of the complex was solved using direct methods by SHELXS-97 program [9].Cadmium atom was located from an E-MAP.The other non-hydrogen atoms were determined with successive difference Fourier syntheses.The final refinement used full-matrix least-squares method by the SHELXL-97 [10].Crystallographic data and refinement parameters are listed in Table 1.Atomic coordinates and selected bond distances and bond angles are given in Tables 2 and 3, respectively.

SUPPLEMENTARY MATERIAL
Detailed crystallographic data in CIF format for the title complex is available from Cambridge Crystallo-graphic Data Center (CCDC reference number: No. 898048).

Table 1 .
Crystal data and structure refinement for the compound 1.

Table 2 .
Atomic coordinates (×104) and equivalent isotropic displacement parameters (A 2 × 10 3 ) for 1. U(eq) is defined as one third of the trace of the orthogonalized Uij tensor.