LABORATORY REPORT OF INORGANIC CHEMISTRYEXPERIMENT 7LIGAND FIELD STRENGTH

Created by:Name : Bunga Mahardhika ANIM : 4301413105Departement : ChemistryProdi : Chemistry EducationLecturer : Ella KusumastutiDate : 17 March 2015Group : 7

DEPARTMENT OF CHEMISTRYFACULTY OF MATHEMATICS AND NATURAL SCIENCESSEMARANG STATE UNIVERSITY2015EXPERIMENT 7Ligand Field Strength

17 March 2015

A. Purpose ExperimentLearn the difference of ligand field strength between ammonia and water

B. TheoryLigand field theory is one of the most useful theory to describe the electronic structure of the complex. Initially this theory is the application of crystal field theory on complex systems. Each ligand, whether it's a neutral molecules or negative ions, donate a pair of electrons to form a bond with the central ion or atom. Style that is held against the central ion or atom by these electrons, and the net charge of ligands, called the ligand field. (Kleinfelter, 1999)Crystal field theory developed by Bethe and Van Vieck. This theory assumes that the interaction between the central ion and ligand only electrostatic interactions. Ion or atom center is seen as positively charged particles, whereas the ligand as negatively charged particles, because in general ligand negatively charged or polar molecules. (Nuryono, 1999)The electric field induced by the ligand will affect the electrons on the central ion and ion induced electric field center also affect the electrons in the surrounding ligands. Electrons on the central ion is most affected by the electric field induced by the ligand is the d orbital electrons, because the d electrons are very instrumental in forming complex ions. (Nuraini S, 1994)Both d orbitals are concentrated along the coordinate axes are dx2 and dx2-y2 and leads directly to ligand charge, will have a higher power compared with the three d orbitals are concentrated among the coordinate axes are dxy, dxz, dyz. In other words, electrons occupy orbitals d will undergo major kebih repulsion of the electrons occupy orbitals d, because the former leads directly to the negative charge, while the so-called then lead to the space between the ligand charges. In terms of the direction of force can be said that the original degenerate d orbitals in the field of free ions or atoms become lost and split into two parts for the case of compound having octahedral shape. (M. Clyde Day, 1993)Group dxy, dxz, dyz called t2g groups and groups dz2 and dx2-y2 called group eg. The difference in energy group t2g and eg expressed in symbols or 10 Dq called crystal field splitting energy which is also the size of the crystal field strength. According to quantum mechanics, the separation of the five d orbitals are not accompanied by changes in energy, thus decreasing orbital energy in the group are those of the lower level should be offset by the excess energy in the group who are at a higher level. (Nuraini S, 1994)

For the case of compound having tetrahedral and planar shape in terms of 4, when the four ligands approach the central ion ligands approach direction is not in line either with a group or with t2g orbital eg orbitals. Separation d orbitals of the metal ions in tetrahedral complexes into its opposite when compared with separation d orbitals in an octahedral complex (eg lower orbital energy of the orbital t2g). The structure of a rectangular planar complex ions can be obtained from the octahedral structure by eliminating ligands contained along the z axis. So the orbital energy dz2, dxz, and dyz repulsion is reduced because a smaller gain. And increased energy orbitals dx2-y2 and dxy. (Nuraini S, 1994)The difference in energy levels that can be big or small depends on several factors, but all of it is defined as 10 Dq. The big difference in this level can be understood that the crystal field theory can explain the difference in the color of the complex. This can be explained in crystal field theory concurrently complex [Ti (H2O) 6] 3+. One electron in the d orbital Ti3 + ions will occupy the lower energy level (t2g). If the complex received a number of energy (light energy) whose energy is equal to the price of 10 Dq, then the energy will be absorbed to excite electrons to a higher level (eg). (Tim Lecturer of Inorganic Chemistry, 2014)The amount of 10 Dq is influenced by the type of metal ions and ligands oxidation numbers involved. Electronic transition from the first energy level to another energy level falls in the region of visible light or electromagnetic spectrum. Visible color is the color of light that is absorbed complement, for example complexes [Ti (H2O) 6] 3+ purple color means the color is absorbed is complementary purple color is yellowish green. The relationship between the wavelength region that is absorbed and colors that look as shown in Table 1.Wavelength (nm)Colors are absorbedComplementary colors (colors that look)

400 435Puple Yellowish green

435 480BlueYellow

480 490Greenish blueOrange

490 500Bluish greenRed

500 560GreenRedish purple

560 580Yellowish greenPuple

580 595YellowBlue

595 610JinggaGreenish blue

610 800RedBluish green

Table 01.(Anonim, 2011)

C. Apparatus and ReagentsApparatus : 10 ml and 50 ml volumetric flask Volumetric pipette 2 ml, 5 ml, 10 ml Beaker glass 100 ml Dropping pipette The test tube rack Test tube Stirring bar Cuvette The glass measuring 10 ml Spectrophotometer Spectronik 20

Reagents: Ammonia solution 1 M Cu 2+ solution of 0.1 M Distilled water

D. Procedure

Cu2+ 0,1M 25% : 75% NH3 1M)(Solution C)Cu2+ 0,1M 50% : 50% NH3 1M)(Solution B)Cu2+ 0,1M(Solution A)

Observed absorption solution A, B, C using Genesys 20 spectrophotometer at a wavelength of 550-700 nm with an interval of 10nm.

Comparing the maximum wavelength to determine the strength of the ligand field.

E. Observation DataNo. (nm)Absorbance Cu2+ (water)Absorbance Cu2+ (50 water : 50 ammonia)Absorbansi Cu2+ (25 water : 75 amonia)

1.5500,0230,9721,858

2.5600,0311,0792,051

3.5700,0411,1642,199

4.5800,0541,2282,301

5.5900,0731,2392,053

6.6000,0951,2602,079

7.6100,1221,2612,075

8.6200,1571,2462,062

9.6300,1941,2202,038

10.6400,2451,1801,993

11.6500,3041,1311,939

12.6600,3741,0761,866

13.6700,4451,0191,782

14.6800,5270,9531,683

15.6900,6100,8901,581

16.7000,6950,8281,477

17.7100,779

18.7200,866

19.7300,944

20.7401,017

21.7501,081

22.7601,139

23.7701,185

24.7801,218

25.7901,242

26.8001,258

27.8101,263

28.8201,261

29.8301,252

F. Calculation and Discussion Energy of solution Ae = h. e = 6,6.10-34 Js x e = 0,024 x Energy of solution Be = h. e = 6,6.10-34 Js x e = 0,032 x Energy of solution Ce = h. e = 6,6.10-34 Js x e = 0,034 x

In this practicum, conducted experiments about the strength of the ligand field that aims to understand the difference between the ligand field strength of ammonia and water. The difference in the ligand field strength is distinguished by determination of 10 Dq energy. 10 Dq value is the energy needed for the splitting or separation of d orbitals or electrons are excited to higher energy levels when given light energy. This experiment was conducted in 3 variations solution was analyzed using Genesys 20 spectrophotometer with a wavelength of 550 nm to 840 nm and interval 10 nm. This variation consists of solution A, solution B, and solution C. Where solution A is a solution of 0.1 M Cu 2+ complexes with water, solution B is a solution of 0.1 M Cu2+ complexes with water and ammonia solution 1 M, which has a ratio of 50%: 50% , and a solution of C is a solution of 0.1 M Cu 2+ complex with water and ammonia solution 1 M, having ratio of 25%: 75%.The results were observed when each solution is prepared is the formation of colored solutions. The more ammonia contained in the Cu 2+ complex solution then the blue color that looks more dark. This is because the difference in the energy levels of atomic orbitals are bonding in each solution. The colors are characteristic of complex compounds Cu2+. And the colors are complementary colors which are light waves that are not absorbed by the solution. Because only the light waves (with a wavelength) that can be absorbed certain. When the purple blue color that looks so color is absorbed is yellowish green, and blue colors are visible when the color is absorbed is orange.Then, these three solutions would be determined its absorbance by using Genesys 20 spectrophotometer at a wavelength of 550 nm to 840 nm at intervals of 10 nm. This wavelength range is chosen because most transition metal ions absorbancing radiation in the UV region of the spectrum or visible light is about 400nm-700nm. Then, 3 variations of this solution was put into cuvette. This cuvette as a sample to be analyzed with a spectrophotometer. Before analysis we also have to prepare a blank solution. Blank solution is a solution of the same composition as the solution was analyzed but without analyzed samples. Blank solution in these experiments was distilled water. This cuvette should always clean, the exterior should be cleaned and dried prior to use tissue. This is because it is very sensitive spectrophotometer, when the cuvette in a dirty state of the absorption of light by the sample was not optimal so that the data obtained is also not good. Before the sample is measured absorbance, should be measured prior absorbance of the reference solution. Blank solution with zero absorbance and transmittansi 100% (does not absorb radiation), is used as the standard for measuring the absorbance of the complex.Solution A is 3 ml of 0.1 M Cu 2+, color formed in the solution is light blue (almost all of the complex magnitude Dq price equal to the energy frequency spectra lies in the visible region, since no relation between the color with the color of a complex frequency depends on the frequency of the absorbed. the color complex is complementary color light blue complex absorbed. So that, when the compound absorbs the color complements, that is orange color with a maximum wavelength of 810 nm). The maximum wave length obtained is 810 nm, and the value of e in solution A is e = 0,024 x .Absorbed ColorObserved Color

410PurpleYellow-green

430Blue-purpleYellow

480BlueOrange

500Green-blueRed

530GreenRed-purple

Absorbed ColorObserved Color

560Yellow-greenPurple

580YellowBlue-purple

610OrangeBlue

680RedGreen-blue

720Red-purpleGreen

Forming a copper complex compound with the formula [Cu(H2O)6]2 where Cu2+ as the central atom and H2O as the ligand.Electron configuration of copper and copper ions are as follows :Cu : 3d104s24p4dCu2+ :3d104s24p4dCu2+ ions bind to the H2O ligands that undergo hybridization. Hybridization that occurs is sp3d2. Hybridization shape for this type is octahedral. In solution A wavelength is 830 nm obtained. Reaction that occurs in this experiment is :Cu2+ + 6 H2O [Cu(H2O)6]2+In solution B, 3 ml of 0.1 M solution of Cu2+ mix with 3 ml NH3 1M with a ratio of 50%: 50%. This solution produces a deep blue color which is more dense than the solution A. The color is formed in the solution is blue (blue complex absorbs the color complements the complex is orange with a maximum wavelength is 610 nm). The value of e in solution B is e = 0,032 x .

Absorbed ColorObserved color

410PurpleYellow-green

430Blue-purpleYellow

480BlueOrange

500Green-blueRed

530GreenRed-purple

Absorbed ColorObserved Color

560Yellow-greenPurple

580YellowBlue-purple

610OrangeBlue

680RedGreen-blue

720Red-purpleGreen

In this solution, ammonia and water is as the Ligand. The complex compounds that formed are [Cu(H2O)3(NH3)3]2+. The reaction occurs :[Cu(H2O)6]2++ 4NH3 [Cu(H2O)3(NH3)3]2+The results of the above reaction shows that there are 3 ligand NH3 and 3 ligand H2O, so that the electron configuration is :3d4s4p4dFrom the above it can be seen that the orbital hybridization [Cu(H2O)3(NH3)3]2+ is sp3d3 to form octahedral geometry. In solution B, the maximum wave length obtained is 610 nm.In solution C, 2.5 ml of Cu2+ solution 0.1 M mix with 7.5 ml of NH3 solution 1M, with a ratio 25%:75%. The addition of excess ammonia levels will increase the value of the absorbance. The maximum wavelength of 580 nm is obtained. After calculating the energy obtained for e = 0,034 x This solution produces a dark blue color. Color formed in the solution is blue (blue complex then the complex absorbs color is orange to complement the maximum wavelength is 580 nm)

Absorbed ColorObserved Color

410PurpleYellow-green

430Blue-purpleYellow

480BlueOrange

500Green-blueRed

530GreenRed-purple

Absorbed ColorObserved Color

560Yellow-greenPurple

580YellowBlue-purple

610OrangeBlue

680RedGreen-blue

720Red-purpleGreen

In this solution of ammonia and water acts as a ligand. Complex compounds formed are [Cu(H2O)4(NH3)2]2+ with reactions that occur as follows :[Cu(H2O)6]2+ + 4NH3[Cu(H2O)4(NH3)2]2+Hybridization that occurs from the compound [Cu(H2O)4(NH3)2]2+ is sp3d2, the molecular shape is octahedral geometry.Maximum absorbance shows maximum wavelength that is absorbed by the solution of complex compounds. From the experimental results shows that the maximum wavelength highest in solution A (solution of Cu2+) is 810 nm and decreased to 610 nm in solution B (solution of Cu2+ and ammonia 50:50) and dropped again to 580 nm in solution C (solution of Cu2+ and ammonia 25:75). Based on the wavelength obtained 10 Dq energy determined for each solution. 10 Dq The values obtained each solution is :Solution A e = 0,024 x Solution B e = 0,032 x Solution C e = 0,034 x From the experiment results it can be concluded that the sequence of ligand field strength is:Solution C > Solution B > Solution A.These results are consistent with existing theory. According to the order of the strength of the ligand field theory NH3> H2O> Cu2+. 10 Dq value in a solution containing ammonia ligand is greater than the solution containing pure water ligands. This indicates that the ammonia ligand ligand has a stronger force. This happens because the wavelength is shorter than the solution C wavelength solution A and solution B. The ligand field strength (which is marked also by the increasing number of the content of ammonia), the smaller the maximum wavelength that is absorbed (Hk. Lambert Beer) so that the greater 10 Dq values obtained. This happens because of the transition elements have a wide absorption band and is strongly influenced by the environment. Absorption band broadening seen in landainya peak (not conical) formed on the chart each solution can be seen in the graph of determining the maximum wavelength. Top of the chart is formed sloping, not conical. This indicates that the transition elements have absorption bands are widened. But in the experiments of our group is not in accordance with the existing theory, the color of the solution C is dark blue, while the color is dark blue solution B concentrated. Supposedly more ammonia solution is added, the color of the resulting solution was further concentrated. This may occur due to less than perfect shake and shuffle when solution B, there is a solution that is spilled, and the errors are less conscientious practitioner.G. Conclusion and SuggestionConlusion : Crystal field theory shows the interaction between the metal ions Cu2+ with ammonia and water ligands which are electrostatic interactions Ammonia ligand is stronger than water ligand, so that the bonds between Cu 2+ ions with strong ammonia ligands and it is indicated by the high value of 10 Dq obtained along with a number of ammonia contained in the solution. The greater the value of 10 Dq in a solution, the wavelength is shorter. The calculation obtained from the experiment result are :Solution A = 810 nm, e = 0,024 x Solution B = 610 nm, e = 0,032 x Solution C = 580 nm, e = 0,034 x From the experiment results it can be concluded that the sequence of ligand field strength is:Solution C > Solution B > Solution A.

Suggestion : Practitioner should be more careful and meticulous during the practicum Practitioner must understand the procedure and mtheory before doing the practicum The tools that will be used should be in good condition Practitioner should maintain the cohessiveness within the members of the groupH.ReferenceAnonim. 2011. http://wanibesak.wordpress.com/2011/07/04/spektrofotometri-sinar-tampak-visible/ (Diakses pada tanggal 16 Mei pukul 13:50)Nuraini. 2011. http://hikmaharifblog.blogspot.com/ (Diakses pada tanggal 16 Mei 2014 pukul 14:15)Nuryono. 1999. Kimia Koordinasi.Yogyakarta :Lab Kimia Anorganik Jurusan Kimia FMIPAUGM.Silmi. 2011. http://hurulsilmi.blogspot.com/2011/05/kekuatan-medan-ligan.html (Diakses pada tanggal 16 Mei 2014 pukul 14:43)Tim Dosen Kimia Anorganik. 2014. Petunjuk Praktikum Kimia Anorganik. Semarang : Laboratorium Kimia FMIPA UNNES.Vogel.1990. Analisis Anorganik Kualitatif Makro dan Semi Mikro, Jilid 2. Jakarta : PT. Kalman Media Pustaka.

Semarang, 20 March 2015Practitioner

Bunga Mahardhika ANIM. 4301413105

I. Appendix

Documentation of practicum

Solution A Soution B Solution C

4321

Solution in cuvette :1. Blank solution = distilled water2. Solution A = Cu2+ 0,1 M3. Solution B = Cu2+ 0,1 M : NH3 1 M (50:50)4. Solution C = Cu2+ 0,1 M : NH3 1 M (25:75)