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NHM T4V NGC TN HONG XUN THNG V MNH TN NGUYN KHNH TN

I. Gii thiu:

I.1. S lc lch s thuyt trng phi t. I.2. S lc v mt s nh bc hc t nn mng cho thuyt trng phi t. II. Ni dung: II.1.M hnh. II.2. S tch mc nng lng d trong trng tinh th. II.3. nh l Jahn-Teller(1937).

II.4. Cu hnh in t v t tnh ca phc kim loi chuyn tip vi nhiu in t d. II.5. Gii thch nguyn nhn sinh ra ph hp th v mu ca phc cht. III. Hn ch thuyt trng phi t. IV. Ti liu tham kho.

I. GII THIUI.1. S lc lch s thuyt trng phi tBt ngun t thuyt trng tinh th, mi n nhng nm 50 ca th k ny mi c p dng vo phc cht ca kim loi chuyn tip nn c tn l thuyt trng phi t.

I.2. S lc v mt s nh bc hc t nn mng cho thuyt trng phi t:

a) John Hasbrouck Van Vleck (1899-1980).

b/Hans Albrecht Bethe (1906-2005) sinh ra Strassburg, CHLB c c (by gi l Strassbourg, Php)

II. Ni dung

II.1.M hnhTrong phc,cc in t c th coi l c nh c hoc ti ion trung tm hoc ti cc phi t.

M hnh ny c tha nhn l c s cho thuyt trng tinh th, gm ba lun im chnh.d1 Ti3+ d2 V3+ d3 Cr3+ V2+ d4 MN3+ Cr2+ d5 Fe3+ Mn2+ d6 Co3+ Fe2+ d7 Co2+ d8 Ni2+ d9 Cu2+ d10 Cu+ Zn2+

II.2. S tch mc nng lng trong trng tinh th.

II.2.1. Khi qut: Trong nguyn t hay ion t do c nm orbital d u c cng mt mc nng lng nh nhau (suy bin).

II.2.2. Trng phi t bt din Th d in hnh l phc [Ti(H2O)6]3+ (c cu hnh in t d1) Ta c cu hnh cc AO d nh sau:

0 =E(g)-E(t2g). Nu coi E l mc 0 th theo quy tc trng tm ta c: 2E(eg)+3E(t2g)=0 T : E(eg)=+3/50 v E(t2g)=-2/50

II.2.2. Trng phi t t din:

t=4/90

II.2.4. Trng phi t bt din bin dng v vung phng:

Tch mc nng lng trong trng hp hai phi t trn trc z n ion trung tm ln hn khong cch n ion trung tm ca bn phi t khc ( bt din ko di )

i vi trng hp m hai phi t trn trc z ng gn ion trung tm hn(bt din bt)

-Tm li ta c bng tng kt sau:

II.3. nh l Jahn-Teller(1937)

Mt phn t bt k trng thi in t suy bin s l mt h khng bn vng v c khuynh hng bin dng. T dn n s gim tnh i xng ca phn t v s tch cc trng thi suy bin

CuX2 CuF2 CuCl2 CuBr2

Lien ket ngan 0.193 0.230 0.240

Lien ket dai 0.227 0.295 0.38

II.4. Cu hnh in t v t tnh ca phc kim loi chuyn tip vi nhiu in t d:II.4.1 Thng s tch nng lng

II.4.1.1. Khi nim:

Thng s tch nng lng l hiu nng lng ca orbital d cao v orbital d thp

II.4.1.2. Cc yu t nh hng n thng s tch nng lng:-in tch ca ion trung tm. -Kch thc ca ion trung tm.

(M)2+ [CrCl6]413000 [Cr(H2O)6]3+ 14000 [Cr(en)3]2+ 18000

(M)3+ [CrCl6]3[Cr(H2O)]3+ [Cr(NH3)6]3+ [Cr(en)3]3+ [Cr(CN)6]31 3200 17400 21500 21900 26600

(M)3+ Cr2+,Cr3+,Mo3+ [MoCL6]319200

(M)3+

Co2+,Co3+,Rh3+,Ir3+ [Co(H2O)6]2+ 9300 [Co(NH3)6]3+ 10100 [Co(en)3}2+ 11000 [Co(H2O)6]3+ 18200 [Co(NH3)6]3+ 22900 [Co(en)3]3+ 23200 [Co(CN)6]3- 33500 [RhCl6]320000 [Rh(H2O)6]3+ 27000 [Rh(NH3)6]3+ 34100 [Rh(en)3]3+ 34600 [Rh(CN)6]3- 45500 Mn2+,Mn3+ [MnCl6]47500 [Mn(H2O)3]2+ 8500 [Mn(en)3]2+ 10100 [MnCl6]320000 [Mn(H2O)6]3+ 21000 Fe2+,Fe3+ [Fe(H2O)6]2+ [Fe(CN)6]48500 32800 [FeCl6]311000 [Fe(H2O)6]3+ 14300 [Fe(CN)6-]3- 35000 [IrCl6-] 25000 [Ir(NH3)6]3+ 41000 [Ir(en)3]3+ 41400

-Phi t c nh hng mnh n thng s tch NL ca phc cht

II.4.2. Nng lng ghp in tt2g

Nng lng tiu tn trong qu trnh chuyn in t t mt orbital m ch c mt mnh n v mt orbital m c mt in t gi l nng lng ghp in t P

II.4.3. Gii thch t tnh:

> P phc spin thp. < P phc spin cao

Bng nng lng tch v nng lng ghp trung bnh P v trng thi spin ca mt s phc.Cu hnh ion t do d4 d5 d6 d7 ion Cr2+ Mn3+ Mn2+ Fe3+ Fe2+ P [cm-1] 23 500 28 000 25 500 30 000 17 000 Phi t 6H2O 6H2O 6H2O 6H2O 6H2O 6CN6F6NH3 6H2O [cm-1] 13 900 21 000 7 800 13 700 10 400 33 000 13 000 23 000 9 300 Trng thi spin Cao _ _ _ _ Thp Cao Thp Cao

Co3+Co2+

21 00022 500

a)ion Fe2+ t do b)phc [Fe(H2O)6]2+ c)phc [Fe(CN)6]4-

Da vo cu trc electron d trong phc cht.

-Nng lng ca ion trung tm s gim i mt lng no so vi ion trong trng i xng cu,nng lng thay i gi l nng lng an nh tinh th(NATT).

Phc bt din spin cao: NATT=ndt2g*(-2/5o) + ndeg*(+3/5o)

Phc bt din spin thp:NATT=ndt2g*(-2/5o)+ndeg*(+3/5o)+mP m: s cp e ghp i thm so vi ban u

Gii thch tnh oxi ho-kh ca cc hp cht phc. V d 1:Cc phc bt din ca Co2+

Spin thp

Spin cao

Trng thi bo ha

V d 2:phc spin cao ca Fe2+ thng th hin tnh kh manh

-1e

Tnh bn ca cc hp cht phcV d: Tnh bn ca cc phc bt din ca Cr3+

Trong khi phc bt din ca Cr2+Th hin tnh kh mnh

II.5. Gii thch nguyn nhn sinh ra ph hp th v mu ca phc chtMu ca phc chtMu l kt qu ca s hp th mt phn nh sng trng thy.

Bc sng ca Mu ca bc x b hp bc x b th hp th 4000-4350 Tm 4350-4800 Xanh chm 4800-4900 Chm lc 4900-5000 Lc-chm 5000-5600 Lc 5600-5750 Lc-vng 5750-5900 Vng 5900-6050 Da cam 6050-7300 7300-7600 ta

Mu trng thy (mu ph) Vng-lc Vng Da cam ta Tm Xanh chm Chm-lc Lc-chm Lc

Ph hp th

ng cong biu din s bin i ca hp th nh sng theo bc sng c gi l ph hp th.

Nguyn nhn sinh ra ph hp th ca phc cht cc kim loi chuyn tip.Do s chuyn di electron c nng lng thp n d c nng lng cao, thng c gi l s chuyn di d-d.

Xt ph hp th ca ion bt din [Ti(H2O)6]3+

Thng s tch nng lng o =242,8 kJ/mol ca ion phc bt din [Ti(H2O)6]3+

o = hcN/N: s ion (nu xt 1mol ion phc th N=NA=6,023.1023) h=6,625.10-34(J.s); c=3.108(m/s) Vi max=4926A0 0 = 242800J/mol = 242,8 kJ/mol Nu o tnh theo cm-1

o = = 1/

= 1/(4926.10-8 )= 20300 cm-1(1000 cm-1 = 11.96 kJ/mol or 2.86 kcal/mol or 0.124 eV )

i vi nhng ion kim loi chuyn tip c 2 electron tr ln:

S chuyn di electron d-d do nhiu electron nn sinh ra mt s di hp th.i vi phc cht bt din ca nhng KLCT c cu hnh electron d4, d6 v d9, ph hp th ch c mt di.

Ph hp th ca ion phc [Cu(H2O)6]2+:

S thay i mu sc gia hai phc cht cng ion trung tm

V d : s thay th H2O trong phc Ni(H2O)62+ bng NH3 lm bin i mu t lc thnh tm. Nguyn nhn: o tng t 101KJ/mol n 129KJ/mol dn n s chuyn dch ph hp th v pha sng ngn.

Cng mu:

L cng ca di hp th, ph thuc vo mc ngn cm s chuyn di electron d-d. Trong cc quy tc lc la ca ha lng t, quan trng nht l nhng quy tc ngn cm chuyn di electron v spin v v tnh i xng.

Quy tc lc la spin:Ngn cm bt k s chuyn di electron no lm thay i tng spin ca h. V d: ngn cm s chuyn di electron d-d trong phc cht bt din spin cao ca ion trung tm c cu hnh d5(t32ge2g).

Quy tc lc la Laport:Hn ch s chuyn di electron bi tnh i xng ca phc cht.V d FeF63- khng mu nhng FeCl4- c mu vng; Co(H2O)62+ c mu hng rt nht nhng CoCl4- c mu xanh chm m.

nh lut Lambert-Beer:D = Cd =lg(I0/I)

ch ph thuc vo bn cht ca cht trong dung dch. ca phc bt din trong khong 5-500 V d ionTi(H2O)63+ l 5 ca phc t din trong khong 200-5000 V d ca ion CoCl4- l gn 600

III. u khuyt im ca thuyt trng phi tThuyt trng phi t ch cho php gii thch nhng tnh cht ca phc xut pht t ion trung tm (th d ph kh kin, t tnh ca phc). B qua phn lin kt cng ha tr ca lin kt kim loi - phi t trong phn t phc.

IV. Ti liu tham kho

Ha v c Nguyn Th T Nga NXB HQG TPHCM. i xng phn t v ng dng l thuyt nhm trong ha hc o ng Thc NXB GD Ha l I o nh Thc NXB KHKT Ho hc cc nguyn t Hong Nhm NXB KHKT Ho lng t Nguyn nh Hu NXB GD http://www.unine.ch/chim/chw/Chapter%204.html http://www.its.caltech.edu http://www.chemistry.galtech.edu http://www.wellesley.edu/Chemistry/chem341 http://www.chem.uwimona.edu http://www.wou.edu http://www.quantum-chemistry-history.com