Advanced Inorganic Chemistry

Transcription

1 Advanced Inorganic Chemistry Alireza Gorji Department of Chemistry, Yazd University Isomerism 20_441 Isomers (same formula but different properties) ایزومری Structural isomers (different bonds) Stereoisomers (same bonds, different spatial arrangements) Coordination isomerism Linkage isomerism Geometric (cis-trans) isomerism Optical isomerism 2 1

2 ایزومری یونش Ionization Isomerism [CrSO 4 (NH 3 ) 5 ]Cl pentaaminsulfatochromium(iii) chloride [CrCl(NH 3 ) 5 ]SO 4 pentaaminchlorochromium(iii) sulfate 3 ایزومری آب پوشی Hydrated Isomerism 4 2

3 ایزومری اتصال Linkage Isomerism [Co(NH 3 ) 4 (NO 2 )Cl]Cl & [Co(NH 3 ) 4 (ONO)Cl]Cl [Co(SCN)(NH 3 ) 5 ] + & [Co(NCS)(NH 3 ) 5 ] + لیگاندهای دوسردندانه Ambidentate Ligands NCS - NO 2 - R-CONH 2 5 ایزومری اتصال Linkage Isomerism [Co(NH 3 ) 5 (NO 2 )]Cl 2 Pentaamminenitrocobalt(III) chloride [Co(NH 3 ) 5 (ONO)]Cl 2 Pentaamminenitritocobalt(III) chloride 6 3

4 - Electronic effect - Steric effect - Solvent effect - Lattice effect - Counter ion effect 7 8 4

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6 11 ایزومری پلیمری Polymerization Isomerism 12 6

7 Isomerism 20_441 Isomers (same formula but different properties) ایزومری Structural isomers (different bonds) Stereoisomers (same bonds, different spatial arrangements) Coordination isomerism Linkage isomerism Geometric (cis-trans) isomerism Optical isomerism 13 استریوایزومری Stereoisomerism 1- Geometric isomerism 1. Geometric isomerism (cis-trans): Pt(NH 3 ) 2 Cl 2 2. Geometric isomerism (fac-mer): IrH 3 (PR 3 ) 3 Atoms or groups arranged differently spatially relative to metal ion 14 7

8 Geometric Isomerism ایزومری هندسی cis-trans سیس ترانس 15 Geometric Isomerism ایزومری هندسی fac-mer وجهی کمربندی ML 3 X 3 وجهی (facial) fac three identical ligands occupying the corners of a common triangular کمربندی (meridional) mer three identical ligands occupying three consecutive corners of a square plane 16 8

9 تحمیل ایزومری به وسیله لیگاند 17 فقط mer فقط fac استریوایزومری Stereoisomerism 2- Stereoisomerism ایزومری نوری 2- Optical isomerism Chiral Complexes S n S 1 = S 2 =i C n D n 18 9

10 C n D n 19 C n D n 20 10

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15 Presentation of [M(en) 3 ]

16 Chiroptic Techniques Plane and circularly polarized light Definitions of terms Optical rotary dispersion (ORD) Circular dichroism (CD) 31 Types of polarized light Plane polarized light consists two circularly polarized components of equal intensity Two circularly polarized components are like leftand right-handed springs As observed by looking at the source, right-handed circularly polarized light rotates clockwise Frequency of rotation is related to the frequency of the light 32 16

17 optically inactive, n L = n R Plane Polarized Light 33 Plane Polarized Light 34 17

18 Optical Rotation n=c/c v optically inactive, n L = n R optically active, n L n R 35 Optical Rotatory Dispersion (ORD) 180d The observed angle of rotation n (normally 589; the Na D line) L Specific rotation, where d is the path length (cm) and c is the concentrat ion (g/ml) dc -1-1 M Molar rotation [ ] [ M ] (deg M cm ), where M is the MW in grams per mole dc The technique of optical rotatory dispersion (ORD) examines the wavelength dependence of optical activity. n R 36 18

19 The Cotton Effect in ORD Positive Cotton effect Negative Cotton effect 37 Circular Dichroism 38 19

20 Circular Dichroism 39 is therefore the angle between the initial plane of polarization and the major axis of the ellipse of the resultant transmitted light A quantity is defined such that tan is the ratio of the major and minor axis of the ellipse of the transmitted light approximates the ellipticity When expressed in degrees, can be converted to a specific ellipticity [ ] or a molar ellipticity [ ] CD is usually plotted as [ ] specific molar ε l ε r Circular Dichroism ellipticit ellipticit y y θ c' d M 10 3 θ

21 3300 ( ) CD( ) ( ) ( ) For historical reasons, commercial instrument s express CD as "ellipticit y" ( ). L R Optical rotatory dispersion (ORD) and circular dichroism (CD) are mathematically related. If you measure one, you can calculate the other by means of functions called Kronig-Kramers Transforms. 2 o M d o 2 2 o 2 [ M ] o [ ] d o 2 2 o CD is more commonly used than ORD to study molecules. - Better resolution - Better sensitivity. - Easier to assign 41 ORD, CD and UV of Camphor 42 21

22 CD Instrumentation 43 The Cotton Effect 44 22

23 Use of CD and ORD spectra 1- Determination of absolute configuration ( & ) 2- Assignment of Electronic spectra Determination of absolute configuration ( & ) Reference: d 6 low spin 46 23

24 1- Determination of absolute configuration ( & )

25 1- Determination of absolute configuration ( & ) Assignment of Electronic spectra 50 25

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