Octahedral Crystal Field Splitting Why do d-orbitals split in these peculiar ways in presence of Octahedral ligand fields? This interactive instruction animation will explain things for the beginner student of Inorganic Chemistry Title of the concept Dhruv Joshi Department of Chemistry IIT Bombay

INSTRUCTIONS TO ANIMATOR In this IDD, first the master layout and the definitions of components will be shown. After that the slides will be shown in the order which the user will be seeing them. Slides will initially contain some theory and then will have a simple interactive animation. Please follow the order shown, which will help the user understand the concept very well.

Master Layout 1 2 WORKSPACE 3 4 TEXT BOX 1 5

Definitions of the components: 1 1.orbital: These are the regions in an atom where electrons are most likely to be found 2.d-orbitals: These are a certain set of orbitals which are found filled in transition metals like Iron, Copper etc. They are important in the study of Complex compounds, which this IDD is dealing with. The d-orbitals are of two types: t2g and eg 3.Complex compounds: compounds made most commonly by Transition metals (like iron, copper, nickel) which involve special bonds, and hence these are classified seperately as complex””. 4.Ligands: These are negatively charged compounds which attach to a transition metal to make complex compounds 2 3 4 5

Analogy / Scenario / Action 1 Analogy / Scenario / Action 2 In forming a complex compound, the d-orbitals of a transition metal undergo some changes which cause the complex compounds to have the unique properties which they do. The so-called “Crystal Field Theory” explains this by electronic repulsion between ligands and the electrons in d-orbitals. The ligands approach the metal from different directions, and depending on which orbital is closest to their direction of approach, they cause the energy of it to increase, due to electronic repulsions. 3 4 5

Slide 1 dxy dyz dxz dx2-y2 dz2 The ligands approaching a transition metal split the d-orbitals in different ways depending on their orientation in space. Please choose one orbital type to know how the degenerate d-orbitals get split in an octahedral field: THESE ARE BUTTONS THAT THE USER CAN CLICK WHICH WILL TAKE THEM TO DIFFERENT INTERACTIVE ANIMATIONS dxy dyz dxz dx2-y2 dz2

3 OPTION 1: dxy SLIDE 1 1 2 4 5 Action Description Audio Narration 3d rotation possible The user is able to move the entire workspace in 3-dimensions by moving the mouse. The various views of the workspace are shown at the bottom, with respect to the three axes (x,y,z) TEXT box 1 In this orbital, four lobes point along the OCTAHEDRAL CASE - dxy 2 3 4 5

ENLARGED VIEW OF THE PARTS – FOR ANIMATOR The three axes X,Y and Z are perpendicular to one another, they are white in colour and will be thin lines. For purposes of reference for the user, the “Z-axis” will be in dashed form, as shown. Against each axis the letters “X”,”Y” or “Z” against the axes indicate which axes it is. The blue and red lobes are solid structures, which are oblong in shape. The sections of these shapes are given below, and in each subsequent case they will be given: The side views along two axes at a time are shown below: This can help build a 3D view of these objects.

3 OPTION 1: dxy SLIDE 2 1 2 4 5 Action Description Audio Narration 3d rotation possible The user is able to move the entire workspace in 3-dimensions by moving the mouse Appearance of the ligands The six spheres appear as shown Energy shift The thick white line in the energy diagram rises slightly as shown OCTAHEDRAL CASE - dxy 2 3 4 5

3 OPTION 1: dxy SLIDE 3 1 2 4 5 Action Description Audio Narration 3d rotation possible The user is able to move the entire workspace in 3-dimensions by moving the mouse Ligand movement The ligands move along the axes to the positions shown Energy shift The thick white line in the energy diagram moves upwards as shown, along with the movement of the ligands TEXT BOX 1 The energy of the orbitals gets lowered since the ligands do not come in direct contact with the orbitals in the course of their movement The energy of the orbitals in this case increases, but to a small extent than the eg orbitals Because the ligands do not repel the orbitals directly, since the lobes are not in the direction of the axes. This energy which has been lost is used to increase the energy of the eg orbitals OCTAHEDRAL CASE - dxy 2 3 4 5

3 OPTION 2: dyz SLIDE 1 1 2 4 5 Action Description Audio Narration 3d rotation possible The user is able to move the entire workspace in 3-dimensions by moving the mouse OCTAHEDRAL CASE - dyz 2 3 4 5

3 OPTION 2: dyz SLIDE 2 1 2 4 5 Action Description Audio Narration 3d rotation possible The user is able to move the entire workspace in 3-dimensions by moving the mouse Ligands appear The six spheres appear as shown, and start moving along the axes directions, towards the centre. Text box 1 text appears “In an octahedral field, the ligands can be considered to be moving along the three orthogonal axes.” Thick white line The thick white line in the energy diagram rises slightly OCTAHEDRAL CASE - dyz 2 3 4 5

3 OPTION 2: dyz SLIDE 3 1 2 4 5 Action Description Audio Narration 3d rotation possible The user is able to move the entire workspace in 3-dimensions by moving the mouse Ligand movement The ligands move along the axes to the positions shown Energy shift The thick white line in the energy diagram moves upwards as shown, along with the movement of the ligands TEXT BOX 1 The energy of the orbitals gets lowered since the ligands do not come in direct contact with the orbitals in the course of their movement The energy of the orbitals in this case increases, but to a small extent than the eg orbitals Because the ligands do not repel the orbitals directly, since the lobes are not in the direction of the axes. This energy which has been lost is used to increase the energy of the eg orbitals OCTAHEDRAL CASE - dyz 2 3 4 5

3 OPTION 3: dxz SLIDE 1 1 2 4 5 Action Description Audio Narration 3d rotation possible The user is able to move the entire workspace in 3-dimensions by moving the mouse OCTAHEDRAL CASE - dxz 2 3 4 5

3 OPTION 3: dxz SLIDE 2 1 2 4 5 Action Description Audio Narration 3d rotation possible The user is able to move the entire workspace in 3-dimensions by moving the mouse Ligands appear The six spheres appear as shown, and start moving along the axes directions, towards the centre. Text box 1 text appears “In an octahedral field, the ligands can be considered to be moving along the three orthogonal axes.” Thick white line The thick white line in the energy diagram rises slightly OCTAHEDRAL CASE - dxz 2 3 4 5

3 OPTION 3: dxz SLIDE 3 1 2 4 5 Action Description Audio Narration 3d rotation possible The user is able to move the entire workspace in 3-dimensions by moving the mouse Ligand movement The ligands move along the axes to the positions shown Energy shift The thick white line in the energy diagram moves upwards as shown, along with the movement of the ligands TEXT BOX 1 The energy of the orbitals gets lowered since the ligands do not come in direct contact with the orbitals in the course of their movement The energy of the orbitals in this case increases, but to a small extent than the eg orbitals Because the ligands do not repel the orbitals directly, since the lobes are not in the direction of the axes. This energy which has been lost is used to increase the energy of the eg orbitals OCTAHEDRAL CASE - dxz 2 3 4 5

3 OPTION 4: dx2-y2 SLIDE 1 1 2 4 5 Action Description Audio Narration 3d rotation possible The user is able to move the entire workspace in 3-dimensions by moving the mouse. The various views of the workspace are shown at the bottom, with respect to the three axes (x,y,z) TEXT box 1 In this orbital, four lobes point along the x and y axes 1 OCTAHEDRAL CASE - dx2-y2 2 3 THIS SHOWS THE ENERGY OF THE ORBITALS IN THE COURSE OF THE ANIMATION, TO SHOW TO THE USER HOW IT CHANGES. THE ENLARGED VERSION OF THIS IS SHOWN IN THE NEXT SLIDE. 4 5

ENLARGED VERSION OF THE ENERGY PROFILE ANIMATOR: This applies to all the slides. The thick line moves upwards or downwards, the rest of the energy diagram stays the same. How the thick line moves will be explained in the “actions” table of each case.

3 OPTION 4: dx2-y2 SLIDE 2 1 2 4 5 Action Description Audio Narration 3d rotation possible The user is able to move the entire workspace in 3-dimensions by moving the mouse Ligands appear The six spheres appear as shown, and start moving along the axes directions, towards the centre. Text box 1 text appears “In an octahedral field, the ligands can be considered to be moving along the three orthogonal axes.” Thick line gets raised slightly. The thick white line in the energy diagram rises slightly above the line marked “barycentre” on which it was initally resting OCTAHEDRAL CASE - dx2-y2 2 3 4 5

3 OPTION 4: dx2-y2 SLIDE 3 1 2 4 5 Action Description Audio Narration 3d rotation possible The user is able to move the entire workspace in 3-dimensions by moving the mouse Ligand effect The four spheres become redder as shown Text box 1 text appears The lobes of the orbitals along the direction of the X and Y axes will experience direct repulsion from the negatively-charged ligands “As can be seen, the lobes of the orbitals along the direction of the X and Y axes will experience repulsion from the negatively-charged ligands. So the energy of the dx2-y2 increases much higher, since they are directly in line.” Thick line The thick white line in the energy diagram moves upwards, along with the movement of the balls towards the centre OCTAHEDRAL CASE - dx2-y2 2 3 4 5

3 OPTION 5: dz2 SLIDE 1 1 2 4 5 Action Description Audio Narration 3d rotation possible The user is able to move the entire workspace in 3-dimensions by moving the mouse. The various views of the workspace are shown at the bottom, with respect to the three axes (x,y,z) TEXT box 1 In this orbital, there is a ring around two central lobes (in the xy plane) which is seperated by a nodal region from two lobes (shown in blue) which point along the positive and negative z-axes In this orbital, four lobes point along the x and y axes 1 OCTAHEDRAL CASE – dz2 2 3 4 5

3 OPTION 5: dz2 SLIDE 2 1 2 4 5 Action Description Audio Narration 3d rotation possible The user is able to move the entire workspace in 3-dimensions by moving the mouse Ligands appear The six spheres appear as shown, and start moving along the axes directions, towards the centre. Text box 1 text appears “In an octahedral field, the ligands can be considered to be moving along the three orthogonal axes.” Thick line gets raised slightly. The thick white line in the energy diagram rises slightly above the line marked “barycentre” on which it was initally resting OCTAHEDRAL CASE – dz2 2 3 4 5

3 OPTION 5: dz2 SLIDE 3 1 2 4 5 Action Description Audio Narration 3d rotation possible The user is able to move the entire workspace in 3-dimensions by moving the mouse Ligand effect The six spheres become redder as shown, as they move closer and closer to the centre. The 2 spheres along the z-axis become redder than the others. Text box 1 text appears The lobes of the orbitals along the direction of the axes will experience direct repulsion from the negatively-charged ligands, especially the ones pointing along the Z-axis. As can be seen, the lobes of the orbitals along the direction of the Z axis will experience much higher repulsion from the negatively-charged ligands, while the ring will experience some repulsion. So the energy of the dz2 increases as much as the dx2-y2 orbitals Thick line The thick white line in the energy diagram moves upwards, along with the movement of the balls towards the centre OCTAHEDRAL CASE – dz2 2 3 4 5

Links for further reading Reference websites: http://www.chemtube3d.com/orbitals-d.htm Books: Research papers: