The allowed UV symmetry transitions for PF5 (a D3h molecule) are A1g, B1g, and B2g. Explain why these three are allowed.
There are actully two main slection rules for electronic transmissions,
1) spin selection rule:- delta S=0 i.e transition to same state ( both spins having same sign) is forbidden.
2) laporte selection rule:- for any molecule posessing a centre of inversion, transition between two "g" states or two "u"states are forbidden. threre should be a change in parity. i.e g-u or u-g transitions are allowed and g-g or u-u are forbidden.
the structure of PF5 is trigonal bipyramidal and has D3h symmetry. and has an inversion centre,the possible transitions are pi-pi* and n-pi* transitions. the allowed symmetry trnsitions are A1g,B1g and B2g. because,
1) In case of molecules without centre of inversion, the electronic transition should give symmetric irreducible representations Ag for allowed trasitions
2)there is a term called transition moment and transition moment integral. transition moment is usually denoted as the electric dipole moment associated with initial and final states,if it is zero then the transition is forbidden.
3) if transition moment integral is zero then the transition are not allowed.
here only A1g,B1g nad B2g yeild non zero transition moment and transition moment integral.
The allowed UV symmetry transitions for PF5 (a D3h molecule) are A1g, B1g, and B2g. Explain...
By considering the effect of each symmetry operation of the D3h point group on the symmetric deformation mode shown in Fig. 3.14, confirm that this mode has A2’’ symmetry. Symmetric stretch 4.7 IR inactive Symmetric deformation IR active (49cm ) Asymmetric stretch IR active 19cm Doubly degenerate mode Asymmetric deformation (E) IR active (Mem') Doubly degenerate mode Fig. 3.14 The vibrational moxdes of SO, D k only three are IR active. The + and holation is used to show the...
for molecule HOOH (C2h symmetry), please find all vibrational modes with allowed fundamental transition.
a) What kind of low-UV/visible light electronic transitions are these molecules expected to have: MLCT, LMCT, LF transitions (two types: spin allowed orbit forbidden; spin and orbit allowed), or none (1.e. none if all transitions are spin forbidden)? For practice, determine the point group. i. [Ru(bipy):12+ ii. [Co(NH3)6]2+ iii. [Mn(OH2)6]2+ iv. [V(OH2)s(O)]+ V. [Ti(C1)4] vi. [Cu(NH3)4]**
The polarity of a molecule is determined by the electronegativity difference in bonds and the symmetry of the overall molecule. Explain why. A. True B. False
1. The molecules PF5 and AsF5 exist, but the analogous molecule NF5 does not. Why not? 2. For the molecule N2O there are five unique Lewis structures that satisfy the octet rule. Three have the N-N-O bond skeleton and two would have the N-O-N skeleton. a) Draw the five UNIQUE Lewis structures. b) By considering the formal charges, can you suggest which structures could be eliminated due to low stability (i.e. have like charges next to each other). c) Which...
5. PF5, shown below, is a trigonal bipyramidal molecule that has been described as “hypervalent” because it exceeds its valence octet. It has been observed that the axial ligands in such molecules must be electronegative. One molecular orbital description for this behaviour invokes the concept of a “three-centre four-electron bond” connecting the axial ligands. Is this model concept consistent with the requirement for electronegative axial ligands? Explain. (Hint: a molecular orbital diagram might help). 900 120°
15. Which of the following electronic transitions in an atom would be allowed? (The designations in parentheses give information on the nature of the electronic transition). Give reasons for why the transition is allowed or not allowed. 'P (3d)+ 'D(4p) *G(3d) + F(3d) 2P (4p) →’S (40) 3 p²s
To what orbitals may a 2p electron in H atom make electric-dipole allowed radiative transitions and explain.
Is this molecule UV active? Why or why not? CHa OH HIC -CH3
Use Web Mo for (pyrazine (C4H4N2)) Point group is D2h (a) Identify and clearly sketch by hand the symmetry elements of the molecule. (b) Calculate the number of degrees of freedom and number of vibrations for the molecule. (c) Determine how the degrees of freedom of the molecule are distributed amongst the irreducible representations of the point group show clearly all your working. (d) Subtract the translations and rotations and hence determine how the normal vibrations of the molecule are...