Crystal structure of aqua-octakis( μ 3 -salicylato)- (1,10-phenanthroline)-(acetonitrile)-dicobalt(II)- trititanium(IV), C 70 H 45 N 3 O 25 Co 2 Ti 3

C 70 H 45 N 3 O 25 Co 2 Ti 3 , triclinic, P 1 (no. 2), a = 12.7748(10) Å, b = 14.7615(11) Å, c = 18.8142(14) Å, α = 99.929(4) ° , β = 92.995(4) ° , γ = 109.170(4) ° , V = 3278.3(4) Å 3 , Z = 2, R gt ( F ) = 0.0383, wR ref ( F 2 ) = 0.1201, T = 296(2) K.


Source of material
In this work, both the reagents and solvents were obtained commercially and used without any purification.
In the first step, a mixture of salicylic acid (2 mmol, 0.276 g), 1,10-phenanthroline (Phen) (0.2 mmol, 0.036 g) and cobalt(II) acetate tetrahydrate (0.3 mmol, 0.075 g) were placed in a teflon-lined stainless vessel (15 mL) and acetonitrile (8 mL) was added as solvent.Then the above mixture was stirred for 10 min and Ti(O i Pr) 4 (0.6 mmol, 0.2 mL) was added in drops.Secondly, the resulting mixture was sealed and heated at 373 K for 48 h under autogenous pressure.Finally, the above teflon-lined stainless vessel was cooled to room temperature at a rate of 5 K h −1 , red and block crystals were obtained and washed with acetonitrile.The yield was 0.122 g (51 %, based on cobalt(II) acetate tetrahydrate).

Experimental details
H atoms were subsequently treated as riding atoms with distances O-H = 0.81 and 0.93 (ArH) Å.

Comment
The metal-doped titanium dioxide (M-TiO 2 ) materials can absorb larger-range sunlight and show higher photocatalytic properties than TiO 2 , which have been widely investigated in the past decades [5][6][7].However, the photocatalytic   mechanisms of M-TiO 2 materials are usually difficult to be illustrated clearly because of their imprecise surface structures [8,9].In the recent years, the metal-doped titaniumoxo clusters (M-TOCs) which can be obtained atom-precise structures by X-ray crystallographic methods have attracted great attention because they can be used as structure and reactivity models for M-TiO 2 [10,11].To date, both the number and structure diversities of M-TOCs are still relatively low.Then, it is important to synthesize more novel M-TOCs.As is known, salicylic acid is a promising ligand for TOCs construction due to its rich coordination patterns and rigid structure [12,13].Herein, salicylic acid was selected as ligand to react with cobalt(II) acetate and titanium isopropoxide to construct cobalt-doped TOCs.A Ti 3 Co 2 corebased M-TOC has been successfully synthesized and structurally characterized.
The molecular formula of the title TOC was written as [Ti 3 Co 2 (salicylate) 8 (Phen)(CH 3 CN)(H 2 O)].The titanium-oxo cluster structure consists of three Ti(IV) ions, two Co(II) ions, eight salicylate groups, one Phen, one CH 3 CN and one H 2 O group (the figure).Each Ti(IV) ion shows the same octahedral [TiO 6 ] coordination environment, and the six coordinated oxygen atoms are all from salicylate groups.It should be pointed out that the two Co(II) ions adopt different coordination modes.One Co(II) ion is five-coordinated featuring [CoO 3 N 2 ] coordination environment, in which the coordinated oxygen atoms are from salicylate groups and the coordinated nitrogen atoms are from a phen group.To be noted, the other Co(II) ion is six-coordinated featuring [CoO 5 N 1 ] coordination environment, among which one water molecule and one acetonitrile participate in coordination.Among the eight salicylate groups, seven of them adopt μ 3 -η 1 :η 1 :η 1 coordination mode, and only one of them adopts μ 3 -η 2 :η 1 :η 1 coordination mode.The three Ti(IV) ions and two Co(II) ions are connected by eight salicylate groups forming the Ti 3 Co 2 core.The bond lengths of Ti-O are in the range of 1.8262(13)-2.0524(13)Å.The bond lengths of Co-O and Co-N are in the range of 2.0025( 14)-2.2757(12)Å and 2.1099(15)-2.1979(17)Å respectively, which are in consistence with the literature [14].There are classical intramolecular hydrogen bonds of O-H⋯O in the structure.This work will provide new strategies for the synthesis of other divalent metal-doped TOCs.

Table  :
Data collection and handling.

Table  :
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å  ).