Presentation on theme: "Physical Methods in Inorganic Chemistry or How do we know what we made"— Presentation transcript:
1 Physical Methods in Inorganic Chemistry or How do we know what we made and does it haveinterestingproperties?
2 What is electronic spectroscopy? Absorption of radiation leading to electronic transitions within a molecule or complexAbsorptionAbsorption[Ru(bpy)3]2+[Ni(H2O)6]2+10410~14 00025 00050 000200400700visibleUVUVvisiblen / cm-1 (frequency)-l / nm (wavelength)UV = higher energy transitions - between ligand orbitalsvisible = lower energy transitions - between d-orbitals of transition metals- between metal and ligand orbitals
3 Absorption maxima in a visible spectrum have three important characteristics number (how many there are)This depends on the electron configuration of the metal centre2. position (what wavelength/energy)This depends on the ligand field splitting parameter, Doct or Dtet and on the degree of inter-electron repulsionintensityThis depends on the "allowedness" of the transitions which is described by two selection rules
4 [Ti(OH2)6]3+ = d1 ion, octahedral complex Absorption of light[Ti(OH2)6]3+ = d1 ion, octahedral complexwhite lightnm3+Tiblue: nmyellow-green: nmred: nmAThis complex is has a light purple colour in solution because it absorbs green lightl / nmlmax = 510 nm
5 [Ti(OH2)6]3+ lmax = 510 nm Do is 243 kJ mol-1 20 300 cm-1 The energy of the absorption by [Ti(OH2)6]3+ is the ligand-field splitting, DoESESegeghnDoGSGSt2gt2gd-d transitioncomplex in electronicGround State (GS)complex in electronicexcited state (ES)[Ti(OH2)6]3+ lmax = 510 nm Do is 243 kJ mol-1cm-1An electron changes orbital; the ion changes energy state
6 d2 ionElectron-electron repulsionegegz2x2-y2z2x2-y2t2gt2gxyxzyzxyxzyzxy + z2xz + z2zzyyxxlobes overlap, large electron repulsionlobes far apart, small electron repulsionThese two electron configurations do not have the same energy
7 Transition e complexes Selection RulesTransition e complexesSpin forbidden 10-3 – 1 Many d5 Oh complexesLaporte forbidden [Mn(OH2)6]2+Spin allowedLaporte forbidden 1 – 10 Many Oh complexes[Ni(OH2)6]2+10 – 100 Some square planar complexes[PdCl4]2-100 – coordinate complexes of low symmetry, many square planar complexes particularly with organic ligandsSpin allowed 102 – 103 Some MLCT bands in cxs with unsaturated ligandsLaporte allowed102 – 104 Acentric complexes with ligands such as acac, or with P donor atoms103 – 106 Many CT bands, transitions in organic species
8 e Tanabe-Sugano diagram for d2 ions 10 000e30 000n / cm-1-1020 0005[V(H2O)6]3+: Three spin allowed transitionsE/B= 32n1 = cm-1 visiblen2 = cm-1 visiblen3 = obscured by CT transition in UVD/B = 32n3 = 2.1n1 = 2.1 x n3 = cm-1= 1.4417 800D/B
11 macroscopic world N S A pioneering experiment by M. Faraday « Farady lines of forces »about magnetic fluxNS
12 macroscopic world« traditional » magnetsNSNSattractionNS
13 macroscopic world« traditional » magnetsNSNSrepulsionNS
14 macroscopic world looking closer to the magnetic domains S N manysets ofdomainsmanysets ofatomicmagneticmoments
15 The magnetic moments order at Curie temperature A set of molecules / atoms :Solid, Magnetically Orderedthermal agitation (kT) weakerthan the interaction (J)between molecules… Paramagnetic solid : thermal agitation (kT) larger than the interaction (J) between moleculesTCkT ≈ JMagnetic OrderTemperatureor CuriekT << JkT >> J
16 ferro-, antiferro- and ferri-magnetism Magnetic Order :ferro-, antiferro- and ferri-magnetism+=Ferromagnetism :Magnetic momentsare identicaland parallel+=Ferrimagnetism (Néel) :Magnetic momentsare differentand anti parallel+= 0Antiferromagnetism :Magnetic momentsare identicaland anti parallel
17 Origin of Magnetism … the electron everything, tiny, elementary I am an electron• rest mass me,• charge e-,• magnetic moment µBeverything, tiny, elementary
18 µtotal = µorbital + µspin Origin of Magnetism« Orbital » magnetic moment« Intrinsic » magnetic momentµorbitaldue to the spins = ± 1/2µspine-µorbital = gl x µB xµspin = gs x µB x s ≈ µBµtotal = µorbital + µspin
19 Dirac Equation 1905 1928 The Principles of Quantum Mechanics, 1930 Nobel Prize 193319051928Equation (10) can be regarded as the Schrödinger equation for an electron interactiong with fields describable by the potentials A and j .
20 Electron : particle and wave Wave function or « orbital » n, l, ml …l =spdangular representation
21 Electron : also an energy level OrbitalsEnergyEmptySingly occupiedDoubly occupied
22 Electron : also a spin ! Up Singly occupied Doubly occupied Down « Paramagnetic »S = ± 1/2« Diamagnetic »S = 0
23 Moleculesare most often regardedas isolated, non magneticDihydrogendiamagneticSpin S = 0
24 the dioxygen that we continuously breath is a magnetic molecule orthogonal πmolecularorbitalsparamagnetic, spin S =1Two of its electrons have parallel magnetic moments that shapesaerobic life and allows our existence as human beings
Your consent to our cookies if you continue to use this website.