• Bulletin of the Korean Chemical Society
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• 제34권4호
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• pp.1055-1060
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• 2013

The adsorption structures of threonine on the Ge(100) surface were investigated using core-level photoemission spectroscopy (CLPES) in conjunction with density functional theory (DFT) calculations. CLPES measurements were performed to identify the experimentally preferred adsorption structure. The preferred structure indicated the relative reactivities of the carboxyl and hydroxymethyl groups as electron donors to the Ge(100) surface during adsorption. The core-level C 1s, N 1s, and O 1s CLPES spectra indicated that the carboxyl oxygen competed more strongly with the hydroxymethyl oxygen during the adsorption reaction. Three among six possible adsorption structures were identified as energetically favorable using DFT calculation methods that considered the inter- and intra-bonding configurations upon adsorption onto the Ge(100) surface. These structures were O-H dissociated N dative inter bonding, O-H dissociated N dative intra bonding, O-H dissociation bonding. One of the adsorption structures: O-H dissociated N dative inter bonding was predicted to be stable in light of the transition state energies. We thus confirmed that the most favorable adsorption structure is the O-H dissociated N dative-inter bonding structure using CLPES and DFT calculation.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.367-367
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• 2010

The adsorption configurations of S-proline on Ge(100) were studied using scanning tunneling microscopy (STM), density functional theory (DFT) calculations, and high-resolution core-level photoemission spectroscopy (HRCLPES). We identified three adsorption structures of S-proline on Ge(100) through analysis of the STM images, DFT calculations, and HRCLPES results: (i) an 'intrarow O - H dissociated and N dative bonded structure', (ii) an 'O - H dissociation structure', and (iii) an 'N dative bonded structure'. Moreover, because adsorption through the N atom of S-proline produces a new chiral center due to symmetry reduction by N dative bonding, the adsorption configurations have either (R,S) or (S,S) chirality, yielding an (R,S)-'intrarow O - H dissociated and N dative bonded structure' and an (R,S)-'N dative bonded structure', with a preference for reaction at the Re face. This work presents a novel method for generating stereoselective attachment using S-proline molecules adsorbed onto a Ge(100) surface.

• 한국진공학회지
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• 제15권1호
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• pp.50-56
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• 2006

[ $Si(5\;5\;12)-2{\times}1$ ] 표면에 벤젠과 피리딘의 흡착구조를 80K 온도에서 주사 터널링 현미경과 density functional theory 계산 방법으로 연구했다. 벤젠 분자는 기울어진 butterfly 형태로 $Si(5\;5\;12)-2\times1$의 D2, D3 유닛에 두 개의 adatom과 강하게 결합된다. 흡착 벤젠 분자에 두 개의 C=C 이중 결합이 있으며 탄소와 Si adatom 사이에 $di-\sigma$ 결합이 있다. 피리딘 분자는 Si-N dative 결합 또는 $di-\sigma$ 형태로 D2와 D3 유닛의 adatom과 결합을 한다 질소 원자의 홀전자쌍에 의해 결합된 dative 결합은 수직 형태의 구조를 띠며 $di-\sigma$ 결합보다 더 안정한 것으로 나타났다. $Di-\sigma$ 결합은 Si-C2와 Si-C5 또는 Si-Nl와 Si-C4으로 형성된다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.212-212
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• 2012

The Coverage dependent attachment of multifunctional groups included in threonine molecules adsorbed to Ge (100)$-2{\times}1$ surface was investigated using core-level photoemission spectroscopy (CLPES) and density functional theory (DFT) calculations. The core-level spectra at a low coverage indicated that the both carboxyl and amine groups participated in the bonding with the Ge (100) surface by "O-H dissociated and N-dative bonded structure". However, at high coverage level, additional adsorption geometry of "O-H dissociation bonded structure" appeared possibly to minimize the steric hindrance between adsorbed molecules. Moreover, the C 1s, N 1s, and O 1s core level spectra confirmed that the carboxyl oxygen is more competitive against the hydroxymethyl oxygen in the adsorption reaction. The adsorption energies calculated using DFT methods suggested that four of six adsorption structures were plausible. These structures were the "O-H dissociated-N dative bonded structure", the "O-H dissociation bonded structure", the "Om-H dissociated-N dative bonded structure", and the "Om-H dissociation bonded structure" (where Om indicates the hydroxymethyl oxygen). These structures are equally likely, according to the adsorption energies alone. Conclusively, we investigate in threonine on Ge (100) surface system that the "O-H dissociated-N dative bonded structure" and the "O-H dissociation bonded structure" are preferred at low coverage and high coverage.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.216-216
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• 2011

We will investigate the bonding configurations of phenylalanine and tyrosine adsorbed on the Ge(100) surface using CLPES and DFT calculations. First, the C 1s, N 1s, and O 1s spectra obtained at 300 K revealed that both the amine and carboxyl groups of phenylalanine and tyrosine concurrently participated in adsorption on the Ge(100) surface without bond breaking using CLPES, depending on the extent of coverage. In the second place, we confirmed that the "O-H dissociated-N dative bonded structure" is the most stable structure implying kinetically favorable structure, and the "O-H dissociation bonded structure" is another stable structure manifesting thermodynamically advantageous structure using DFT calculations. This tendency turns up both phenylalanine and tyrosine, similarly. Furthermore, through the CLPES data and DFT calculation data, we discovered that the "O-H dissociated-N dative bonded structure" and the "O-H dissociation bonded structure" are preferred at 0.30 ML and 0.60 ML, respectively. Moreover, we found that the phenyl ring of phenylalanine is located in axial position to Ge(100) surface, but the phenyl ring of tyrosine is located in parallel to Ge(100) surface using DFT calculations.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.215-215
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• 2011

The bonding configuration and adsorption stability of alanine and leucine adsorbed on Ge(100)-2${\times}$1 surface were investigated and compared using core-level photoemission spectroscopy (CLPES) and density functional theory (DFT) calculations. The bonding configuration, stability, and adsorption energies were evaluated for two different coverage levels. In both cases, the C 1s, N 1s, and O 1s core-level spectra at a low coverage (0.30 ML) indicated that the carboxyl and amine groups participated in bonding with the Ge(100) surface in an "O-H dissociated-N dative bonded structure". At high coverage levels (0.60 ML), both this structure and an "O-H dissociation bonded structure" were present. As a result, we found that alanine adsorbs more easily (lower adsorption energy) than leucine on Ge(100) surfaces due to less steric hindrance of side chain.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2004년도 제26회 학술발표회 초록집
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• pp.61-61
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• 2004

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.137-137
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• 2013

The most stable adsorption structures and their corresponding energies of 4-pyridone, 4-hydroxypyridine, 2-pyridone and 2-hydroxypyridine have been investigated by Density Functional Theory (DFT) calculation method and high-resolution photoemission spectroscopy (HRPES). We confirmed that between the two reaction centers of 4- and 2-pyridone, only O atom of carbonyl functional group can act as a Lewis base and thus, O dative bonding structure is the most stable. On the other hand, we clarified that both the two reaction centers (the cyclic N atom and the O atom of hydroxyl functional group) of 4- and 2-hydroxypyridine (tautomers of 4- and 2-pyridone) can successfully function as a Lewis base. Through the interpretation of the N 1s and O 1s core level spectra obtained using HRPES, we could confirm the electronic structures and bonding configurations of these molecules with a coverage dependence on the Ge(100) surface.

• 대한화학회지
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• 제38권3호
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• pp.241-245
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• 1994

산화성 첨가반응을 이용하여 실라트란(분자내 Si-N고리횡단 상호작용을 갖는 5-배위의 규소화합물)의 규소원자와 주족원소간에 Si-M 결합작용이 있는 새로운 이종다핵 화합물을 합성하려고 시도하였다. 1-브로모실라트란(1a)과 $SnBr_2를 반응시켜 노란색(2a)과 흰색(2b)의 고체 혼합물을 얻었고 용해도 차에 의해 각각을 분리하여 ^1H-NMR, ^{29}Si-NMR, ^{119}Sn-NMR, Mass스펙트럼으로 규명한 결과 노란색 화합물만이 Si-Sn결합을 갖는 것으로 판명되었다. SnBr_2를 1-브로모-3,7,10-트리메틸실라트란(1b)과도 반응시켜 Si-Sn 결합을 갖는 화합물, N[CH_2CH(CH_3)O]_3SiSnBr_3(CH_3OH)_2(3)$을 분리하여 여러가지 방법으로 확인하였다.