Investigation of the New Room Temperature Ionic Liquid of Al(NO3)3.9H2O with Urea CO(NH2)2

Mixing aluminum nitrate nonahydrate with urea produced room temperatures clear colorless ionic liquid with lowest freezing temperature at (1: 1.2) mole ratio respectively. Freezing point phase diagram was determined and density, viscosity and conductivity were measured at room temperature. It showed physical properties similar to other ionic liquids. FT-IR,UV-Vis, 1 H NMR and 13 C NMR were used to study the interaction between its species where CO ــــ Albond was suggested and basic ion [Al(NO3)4]ˉ and acidic ions [Al(NO3)2. xU] + were proposed. Water molecule believed to interact with both ions. Redox potential was determined to be about 2 Volt from – 0.6 to + 1.4 Volt with thermal stability up to 326 .


Introduction:
Ionic liquids can be defined as a new class of solvents, or as salts with the melting point arbitrarily determined to be below 100°C.They are composed of ions and, thus, each IL possesses unique properties that are due to cation and an anion nature [1][2][3][4].However, Room-Temperature Ionic Liquids (RTILs) have been developed to be the basic alternative to the volatile organic compounds(VOC) for being stable chemically and electrochemical, nonflammable, a high ionic density and conductivity, non-volatile, etc. [5].So there are several reasons that ionic liquids are considered as "green solvents" and therefore, the "designer solvent" can be created for many applications, including biotransformation, chemical reactions (e.g.catalysis and hydrogenation), biorefinery concept, extraction and separation, and others [6,7].
A type of ionic liquids is the eutectic solvents, which have interesting solvent properties.The eutectic solvent of a mixture of choline chloride and urea melt at 12 [8,9].A series of ternary deep eutectic solvents made from sugarurea-salt mixtures were also reported as solvents for organic synthesis [10].One of other reported ionic liquids by Abood and co workers, involves the addition of a simple amide to AlCl 3 resulting in the Open Access formation of ionic liquids of the type [AlCl 2 .nAmid]+ [ AlCl 4 ]ˉ [11].The Infrared spectra in the rang (4000-400cm -1 ) were recorded on Fourier Transform Infrared Spectrophotometer, 2006,IR-Prestige 21,Shimadzu 8000.The HANNA instruments H1 9811 in mS/cm using to carry out conductivity measurement, and viscosity measurement were carried out manually, the density measurement was by using bottle size 25 ml.The Instrument for Cyclic voltammogram (CV) recorded using Digi-lvy-Dy2300 Bipotentiostat with Three-electrode system comprising of a platinum plat as working electrode (WE), a platinum disc of 2 mm as the counter electrode (CE) and a silver wire used as a reference electrode (RE).Using CECEL CE7200.Ultraviolet-visible spectrophotometer at room temperature using quartz cells of 1.0cm path length in the range of wavelength 190-900 nm to obtaine electronic spectra.

Materials and Methods
Thermogravimetric analysis using (STA PT-1000) LINSEIS instrument, the heating rate of 10 /min in the range of 25-500 .NMR spectra were recorded on Burker 500M Hz instrument using DMSO-d6 as solvent and TMS as an internal reference.
The elemental analysis (C.H.N) of urea nitrate were carried out by EM-017.mthinstrument.The measurements of the XRD patterns of the combustion products were recorded using a Shimazu XRD-6000 with Cu-Kα radiations.

Preparation of the Ionic Liquid
Aluminum nitrate nonahydrate and urea were used to prepare ionic liquid in different proportions.Solid salts of aluminum nitrate nonahydrate which had a m.p. of 72°Cand urea with 132°C.were mixed, then heated gradually to 85°C for(2-3) hrs., with a continuous mechanically stirring until both melt together providing a colorless and homogeneous liquid.The produced ionic liquid then cooled to room temperature and stored in a sealed container.Samples from this ionic liquid were used for further identifications.

Results and Discussion:
The prepared binary ionic liquid, [Al(NO 3 ) 3 .9H 2 O/urea] was found to have the lowest freezing point at 3 and can be used as an ambient temperature solvent.The molar ratio effect on freezing point is illustrated in Figure .(1).This liquid was found to have a conductivity of 9.09mS cm -1 , density 1.6028 g .cm - and viscosity of 20.579 pois at 25 , Table (1) shows a comparison at between three ionic liquids (ILs) on urea with three different aluminum salts 25 .The effects of temperatures on the density and viscosity of the new ionic liquid (IL) in this work has both density and the viscosity to be decreased with increasing temperature.
Arrhenius plot of viscosity against temperature was accepted by ionic liquid and showed that viscosity dependent on the temperature, this illustrated in Figures (2 to Ionic liquid had the ability to dissolve in polar solvent such as water and ethanol, but did not dissolve in non polar solvents like toluene, ether, and DMSO.The pH of ionic liquid was unexpectedly high Table (1).A variety of analytical techniques were used to identify by new ionic liquid FT-IR, electronic spectra, thermal analysis, electrochemical measurement and NMR which will be explained as below.IR-spectra showed an interaction between the components of ionic liquid.The comparison in vibration frequencies of ionic liquid and aluminum nitrate and urea salts are showed in Table (2).The vibration frequency of carbonyl group ( ) shifted about 34 cm -1 lower than the frequency in free solid urea.The stretching frequencies of (νN-H) of urea also changed with blue shifts (about 30 cm -1 ) for the symmetrical vibration and to red shift for asymmetric vibration the frequency of N-H about 6cm -1 in IL.

Fig.(7): Electronic spectrum of the Ionic Liquid
The electrochemical potential window of ionic liquids of -0.6 to +1.4 represented the difference between the reduction potential limit and oxidation potential limit of its species.Figure (8) showed the scale of electrochemical window for the 1:1.2Al(NO 3 ) 3 .9H 2 O/ Urea, a scale of potential with total electrochemical potential of 2V.In comparison with other ionic liquids, e.g.ChCl/ urea with a potential window of (-1.2 to +1.2), while aqueous systems possessed about 1.23V.It is clear that ionic liquid has higher potential than water.The 1 H NMR spectrum data of ionic liquid showed only one peak at = 5.28 ppm , similarly the free urea gave one peak at 5.6 ppm which can be assigned to (4H; 2NH 2 ) four protons of two symmetric amino groups.The 13 C NMR spectra for free urea and ionic liquid showed a signal band at approximately the same value of C=O, as shown in Fig. (10 and11), the data are listed in Table ( 3).All the previous examination of ionic liquid helped to suggest an equation of ionic liquid formation as follow:
The crystalline solid separated from IL were used taken for further identifications and analysis by X-ray diffraction, FT-IR, 1 H NMR, 13 C NMR, and CHN.The crystalline identified by X-ray diffraction measurement showed the lattice d-spacing of 3.088 with a maximum intensity for 2 = 28.775 .This result agrees with stander dspacing of urea nitrate of 3.10 [14].The spectrum and data of X-ray analysis are shown in Figure (12) and Table (4).This may be attributed to presence of very small amount of ionic liquid adhered to urea nitrate due to difficult separation.IR spectrum showed, the stretching vibration of the carbonyl group at the1647.21cm −1 which can be presented in both ionic liquid and urea nitrate other frequency appeared at 1384.89 cm - 1 was assigned to NO 3 ˉ group which was less broad than the peak in ionic liquid, but when comparing the band of νN-H with that appeared 3460.30cm -1 and 3360.00 cm -1 in urea nitrate, had small blue shift about 15 cm -1 and red shift about 19cm -1 in IL respectively.The stretching vibration band of νC-N which appeared as a sharp and medium band at 1161 cm -1 which were shifted in urea nitrate(UN) to about 5 cm -1 .Fig. (13) and Table (5) shows FT-IR spectrum and the data of urea nitrate.which appeared at = 6.7 ppm.According to this result, it can be deduced that electronic environments of the urea protons changed with the formed urea nitrate [15].Figure (15) shows 13 C-NMR spectrum in which two peaks appeared due to the carbonyl group.The first one in the position 162 ppm belongs to urea nitrate (UN) in high intensity due to the proton bonding in the oxygen side of carbonyl group, while the second small peak is due to impurities [16].

Conclusions:
Clear colorless room temperature ionic liquid was formed by mixing different molar ratio of aluminum nitrate nonahydrate and urea with lowest freezing temperature at 3 in (1 : 1.2) mole ratio.They formed acidic and basic species where aluminum cation interacted with the carbonyl group of urea in the acidic species in analogues to those formed in other aluminum salt / urea ionic liquid.This ionic liquid showed physical properties similar to other ionic liquids with stable redox potential over 2V (-0.6 to +1.4).Water content believed as in aluminum nitrate / urea ionic liquid is not present as free molecules giving an easy prepared water and atmospheric stable liquid for different chemical applications.
Fig. (1):Phase diagram for (Aluminum nitrate with Urea) system plot for t versus mole ratio of aluminum nitrate.

Fig.( 13
Fig.(13):FT-IR spectrum of urea nitrateFigure(14) shows 1 H-NMR of UN in which two peaks, one type of neutral -NH 2 groups at = 5.4 ppm and the other one has a positively charged + NH 2 , which appeared at = 6.7 ppm.According to this result, it can be deduced that electronic environments of the urea protons changed with the formed urea nitrate[15].Figure(15) shows13 C-NMR spectrum in which two peaks appeared due to the carbonyl group.The first one in the position 162 ppm belongs to urea nitrate (UN) in high intensity due to the proton bonding in the oxygen side of carbonyl group, while the second small peak is due to impurities[16].